ATM
Serine-protein kinase ATM (EC 2.7.11.1) (Ataxia telangiectasia mutated) (A-T mutated)
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Leaf senescence is the final stage of leaf development. It is accompanied by the remobilization of nutrients from senescent leaves to developing organs. The occurrence of senescence is the consequence of integrating intrinsic and environmental signals. DNA damage triggered by stresses has been regarded as one of the reasons for senescence. To prevent DNA damage, cells have evolved elaborate DNA repair machinery. The ataxia telangiectasia mutated (ATM) functions as the chief transducer of the double-strand breaks (DSBs) signal. Our previous study suggests that ATM functions in lifespan regulation in [i]Arabidopsis[/i]. However, ATM regulatory mechanism on plant longevity remains unclear. Here, we performed chemical mutagenesis to identify the components involved in ATM-mediated longevity and obtained three dominant mutants [i]satmf1~3[/i], [i]suppressor of atm in fertility[/i], displaying delayed senescence and restored fertility in comparison with [i]atm[/i] mutant. Molecular cloning and functional analysis of SATMF (suppressor of atm in fertility) will help to understand the underlying regulatory mechanism of ATM in plants, and shed light on developing new treatments for the disease Ataxia-telangiectasia.
Keywords
- ATM
- DNA damage
- SATMF
- fertility
- leaf senescence
While therapies targeting deficiencies in the homologous recombination (HR) pathway are emerging as the standard treatment for high grade serous ovarian cancer (HGSOC) patients, this strategy is limited to the ~50% of patients with a deficiency in this pathway. Therefore, patients with HR-proficient tumors are likely to be resistant to these therapies and require alternative strategies. We found that the HR gene Ataxia Telangiectasia Mutated (ATM) is wildtype and its activity is upregulated in HGSOC compared to normal fallopian tube tissue. Interestingly, multiple pathways related to metabolism are inversely correlated with [i]ATM[/i] expression in HGSOC specimens, suggesting that combining ATM inhibition with metabolic drugs would be effective. Analysis of FDA-approved drugs from the Dependency Map demonstrated that ATM-low cells are more sensitive to fenofibrate, a PPARα agonist that affects multiple cellular metabolic pathways. Consistently, PPARα signaling is associated with [i]ATM[/i] expression. We validated that combined inhibition of ATM and treatment with fenofibrate is synergistic in multiple HGSOC cell lines by inducing senescence. Together, our results suggest that metabolic changes induced by ATM inhibitors are a potential target for the treatment of HGSOC.
Keywords
- Biochemistry
- Bioinformatics
- Cancer research
- Cell biology
- Cellular metabolism
- Cellular senescence
- Drug combinations
- Homologous recombination
- Metabolite
- Molecular biology
- PPARa
Previously, we uncovered a novel mechanism in which senescence is controlled by mitochondrial functional recovery upon Ataxia-telangiectasia mutated (ATM) inhibition. However, it remains elusive how ATM controls signaling pathways to achieve restorative effect. In this study, we performed microarray and found that p53 pathway was differentially expressed upon ATM inhibition. We found that ATM inhibition yields senescence amelioration through p53-dependent manner. The restorative effect was also afforded by direct p53 inhibition. Furthermore, mitochondrial metabolic reprogramming via p53 inhibition was a prerequisite for senescence amelioration. Taken together, our data indicated that p53 pathway functions as potential target for ATM-mediated senescence amelioration.
Keywords
- ATM inhibition
- Metabolic reprogrammer
- Mitochondria
- P53
- Senescence alleviation
DNA damage response inhibitors (DDRi) may selectively enhance the inactivation of tumor cells in combination with ionizing radiation (IR). The induction of senescence may be the key mechanism of tumor cell inactivation in this combinatorial treatment. In the current study the effect of combined IR with DDRi on the induction of senescence was studied in head and neck squamous cell carcinoma (HNSCC) cells with different human papilloma virus (HPV) status. The integrity of homologous recombination (HR) was assessed in two HPV positive, two HPV negative HNSCC, and two healthy fibroblast cell cultures. Cells were treated with the DDRi CC-115 (DNA-dependent protein kinase, DNA-pK; dual mammalian target of rapamycin, mTor), VE-822 (ATR; ataxia telangiectasia and Rad3-related kinase), and AZD0156 (ATM; ataxia telangiectasia mutated kinase) combined with IR. Effects on senescence, apoptosis, necrosis, and cell cycle were analyzed by flow cytometry. The fibroblast cell lines generally tolerated IR or combined treatment better than the tumor cell lines. The ATM and ATR inhibitors were effectively inducing senescence when combined with IR. The DNA-PK inhibitor was not an important inductor of senescence. HPV status and HR activity had a limited influence on the efficacy of DDRi. Induction of senescence and necrosis varied individually among the cell lines due to molecular heterogeneity and the involvement of DNA damage response pathways in senescence induction.
Keywords
- ATM
- ATR
- DNA damage response inhibitor
- DNAPK
- HNSCC
- homologous recombination
- ionizing radiation
- kinase inhibitor
- radiosensitivity
- senescence
Senescent cells display senescence-associated (SA) phenotypic programs such as stable proliferation arrest (SAPA) and a secretory phenotype (SASP). Senescence-inducing persistent DNA double-strand breaks (pDSBs) cause an immediate DNA damage response (DDR) and SAPA, but the SASP requires days to develop. Here, we show that following the immediate canonical DDR, a delayed chromatin accumulation of the ATM and MRN complexes coincides with the expression of SASP factors. Importantly, histone deacetylase inhibitors (HDACi) trigger SAPA and SASP in the absence of DNA damage. However, HDACi-induced SASP also requires ATM/MRN activities and causes their accumulation on chromatin, revealing a DNA damage-independent, non-canonical DDR activity that underlies SASP maturation. This non-canonical DDR is required for the recruitment of the transcription factor NF-κB on chromatin but not for its nuclear translocation. Non-canonical DDR further does not require ATM kinase activity, suggesting structural ATM functions. We propose that delayed chromatin recruitment of SASP modulators is the result of non-canonical DDR signaling that ensures SASP activation only in the context of senescence and not in response to transient DNA damage-induced proliferation arrest.
Keywords
- DNA damage response
- MRN complex
- NF-κB
- chromatin
- senescence secretome
ATM is a kinase involved in DNA damage response (DDR), regulation of response to oxidative stress, autophagy and mitophagy. Mutations in the ATM gene in humans result in ataxi A-Telangiectasia disease (A-T) characterized by a variety of symptoms with neurodegeneration and premature ageing among them. Since brain is one of the most affected organs in A-T, we have focused on senescence of neural progenitor cells (NPCs) derived from A-T reprogrammed fibroblasts. Accordingly, A-T NPCs obtained through neural differentiation of iPSCs in 5% oxygen possessed some features of senescence including increased activity of SA-β-gal and secretion of IL6 and IL8 in comparison to control NPCs. This phenotype of A-T NPC was accompanied by elevated oxidative stress. A-T NPCs exhibited symptoms of impaired autophagy and mitophagy with lack of response to chloroquine treatment. Additional sources of oxidative stress like increased oxygen concentration (20 %) and H O respectively aggravated the phenotype of senescence and additionally disturbed the process of mitophagy. In both cases only A-T NPCs reacted to the treatment. We conclude that oxidative stress may be responsible for the phenotype of senescence and impairment of autophagy in A-T NPCs. Our results point to senescent A-T cells as a potential therapeutic target in this disease.
Keywords
- ATM
- Ataxia-telangiectasia
- Autophagy
- Mitophagy
- Neural progenitors
- Oxidative stress
- Senescence
- hiPSCs
NF-κB is a transcription factor activated in response to inflammatory, genotoxic and oxidative stress and important for driving senescence and aging. Ataxia-telangiectasia mutated (ATM) kinase, a core component of DNA damage response signaling, activates NF-κB in response to genotoxic and oxidative stress via post-translational modifications. Here we demonstrate that ATM is activated in senescent cells in culture and murine tissues from [i]Ercc1[/i]-deficient mouse models of accelerated aging, as well as naturally aged mice. Genetic and pharmacologic inhibition of ATM reduced activation of NF-κB and markers of senescence and the senescence-associated secretory phenotype (SASP) in senescent [i]Ercc1 [/i] MEFs. [i]Ercc1 [/i] mice heterozygous for [i]Atm[/i] have reduced NF-κB activity and cellular senescence, improved function of muscle-derived stem/progenetor cells (MDSPCs) and extended healthspan with reduced age-related pathology especially age-related bone and intervertebral disc pathologies. In addition, treatment of [i]Ercc1[/i] mice with the ATM inhibitor KU-55933 suppressed markers of senescence and SASP. Taken together, these results demonstrate that the ATM kinase is a major mediator of DNA damage-induced, NF-κB-mediated cellular senescence, stem cell dysfunction and aging and thus represents a therapeutic target to slow the progression of aging.
Keywords
- ATM
- DNA damage response
- NF-κB
- aging
- cellular senescence
All living organisms are unavoidably exposed to various endogenous and environmental stresses that trigger potentially fatal DNA damage, including double-strand breaks (DSBs). Although a growing body of evidence indicates that DNA damage is one of the prime drivers of aging in animals, little is known regarding the importance of DNA damage and its repair on lifespan control in plants. We found that the level of DSBs increases but DNA repair efficiency decreases as Arabidopsis leaves age. Generation of DSBs by inducible expression of I-PpoI leads to premature senescence phenotypes. We examined the senescence phenotypes in the loss-of-function mutants for 13 key components of the DNA repair pathway and found that deficiency in ATAXIA TELANGIECTASIA MUTATED (ATM), the chief transducer of the DSB signal, results in premature senescence in Arabidopsis. ATM represses DSB-induced expression of senescence-associated genes, including the genes encoding the WRKY and NAC transcription factors, central components of the leaf senescence process, via modulation of histone lysine methylation. Our work highlights the significance of ATM in the control of leaf senescence and has significant implications for the conservation of aging mechanisms in animals and plants.
Keywords
Arabidopsis thaliana
- ATM
- DNA repair
- double-strand breaks
- histone methylation
- leaf senescence
Axitinib is an orally available inhibitor of tyrosine kinases, with high specificity for vascular endothelial growth factor receptors (VEGFRs) 1, 2, and 3. It is approved for the treatment of advanced renal cell carcinoma and is in phase II clinical trials for recurrent glioblastoma (GBM). GBM is a brain tumor peculiar in its ability to induce neoangiogenesis. Since both GBM tumor cells and endothelial cells of tumor vasculature express VEGFRs, Axitinib exerts its inhibitory action on both tumor and endothelial cells. We and others previously demonstrated that Axitinib triggers cellular senescence. In particular, Axitinib-dependent senescence of HUVECs (human umbilical vein endothelial cells) is accompanied by intracellular reactive oxygen species(ROS) increase and early ataxia telangiectasia mutated(ATM) activation. Here we wondered if the presence of glioblastoma tumor cells could affect the HUVEC senescence upon Axitinib exposure. To address this issue, we cocultured HUVECs together with GBM tumor cells in transwell plates. HUVEC senescence did not result in being affected by GBM cells, neither in terms of β galactosidase activity nor of proliferation index or ATM phosphorylation. Conversely, Axitinib modulation of HUVEC gene expression was altered by cocultured GBM cells. These data demonstrate that the GBM secretome modifies HUVECs' transcriptomic profile upon Axitinib exposure, but does not prevent drug-induced senescence.
MeSH Terms
- Ataxia Telangiectasia Mutated Proteins
- Axitinib
- Cell Line, Tumor
- Cellular Senescence
- Coculture Techniques
- Gene Expression Profiling
- Glioblastoma
- Human Umbilical Vein Endothelial Cells
- Humans
- Phosphorylation
Keywords
- Axitinib
- endothelial cells
- glioblastoma
- senescence
Leukocyte telomere length (LTL) is a heritable biomarker of genomic aging. In this study, we perform a genome-wide meta-analysis of LTL by pooling densely genotyped and imputed association results across large-scale European-descent studies including up to 78,592 individuals. We identify 49 genomic regions at a false dicovery rate (FDR) < 0.05 threshold and prioritize genes at 31, with five highlighting nucleotide metabolism as an important regulator of LTL. We report six genome-wide significant loci in or near SENP7, MOB1B, CARMIL1, PRRC2A, TERF2, and RFWD3, and our results support recently identified PARP1, POT1, ATM, and MPHOSPH6 loci. Phenome-wide analyses in >350,000 UK Biobank participants suggest that genetically shorter telomere length increases the risk of hypothyroidism and decreases the risk of thyroid cancer, lymphoma, and a range of proliferative conditions. Our results replicate previously reported associations with increased risk of coronary artery disease and lower risk for multiple cancer types. Our findings substantially expand current knowledge on genes that regulate LTL and their impact on human health and disease.
MeSH Terms
- Genome-Wide Association Study
- Humans
- Leukocytes
- Nucleotides
- Telomere
Keywords
- Mendelian randomisation
- age-related disease
- biological aging
- telomere length
Recent data suggest that paternal age can have major impact on reproductive outcomes, and with increased age, there is increased likelihood of chromosomal abnormalities in the sperm. Here, we studied DNA damage and repair as a function of male aging and assessed whether sphingosine-1-phosphate (S1P), a ceramide-induced death inhibitor, can prevent sperm aging by enhancing DNA double-strand breaks (DSB) repair. We observed a significant increase in DNA damage with age and this increase was associated with a decline in the expression of key DNA DSB repair genes in mouse sperm. The haploinsufficiency of BRCA1 male mice sperm showed significantly increased DNA damage and apoptosis, along with decreased chromatin integrity when compared to similar age wild type (WT) mice. Furthermore, haploinsufficiency of BRCA1 male mice had lower sperm count and smaller litter size when crossed with WT females. The resulting embryos had a higher probability of growth arrest and reduced implantation. S1P treatment decreased genotoxic-stress-induced DNA damage in sperm and enhanced the expressions of key DNA repair genes such as BRCA1. Co-treatment with an ATM inhibitor reversed the effects of S1P, implying that the impact of S1P on DNA repair is via the ATM-mediated pathway. Our findings indicate a key role for DNA damage repair mechanism in the maintenance of sperm integrity and suggest that S1P can improve DNA repair in sperm. Further translational studies are warranted to determine the clinical significance of these findings and whether S1P can delay male reproductive aging. There is mounting evidence that sperm quality declines with age, similar to that of the oocyte. However, the reasons behind this decline are poorly understood and there is no medical intervention to improve sperm quality. Our study suggests a strong role for DNA damage repair in maintenance of sperm quality, and for the first time, a potential pharmaceutical approach to prevent sperm aging.
Keywords
- Aging
- DNA fragmentation
- Gene expression
- Sperm
Oocyte aging has significant clinical consequences, and yet no treatment exists to address the age-related decline in oocyte quality. The lack of progress in the treatment of oocyte aging is due to the fact that the underlying molecular mechanisms are not sufficiently understood. BRCA1 and 2 are involved in homologous DNA recombination and play essential roles in ataxia telangiectasia mutated (ATM)-mediated DNA double-strand break (DSB) repair. A growing body of laboratory, translational and clinical evidence has emerged within the past decade indicating a role for BRCA function and ATM-mediated DNA DSB repair in ovarian aging. Although there are several competing or complementary theories, given the growing evidence tying BRCA function and ATM-mediated DNA DSB repair mechanisms in general to ovarian aging, we performed this review encompassing basic, translational and clinical work to assess the current state of knowledge on the topic. A clear understanding of the mechanisms underlying oocyte aging may result in targeted treatments to preserve ovarian reserve and improve oocyte quality. We searched for published articles in the PubMed database containing key words, BRCA, BRCA1, BRCA2, Mutations, Fertility, Ovarian Reserve, Infertility, Mechanisms of Ovarian Aging, Oocyte or Oocyte DNA Repair, in the English-language literature until May 2019. We did not include abstracts or conference proceedings, with the exception of our own. Laboratory studies provided robust and reproducible evidence that BRCA1 function and ATM-mediated DNA DSB repair, in general, weakens with age in oocytes of multiple species including human. In both women with BRCA mutations and BRCA-mutant mice, primordial follicle numbers are reduced and there is accelerated accumulation of DNA DSBs in oocytes. In general, women with BRCA1 mutations have lower ovarian reserves and experience earlier menopause. Laboratory evidence also supports critical role for BRCA1 and other ATM-mediated DNA DSB repair pathway members in meiotic function. When laboratory, translational and clinical evidence is considered together, BRCA-related ATM-mediated DNA DSB repair function emerges as a likely regulator of ovarian aging. Moreover, DNA damage and repair appear to be key features in chemotherapy-induced ovarian aging. The existing data suggest that the BRCA-related ATM-mediated DNA repair pathway is a strong candidate to be a regulator of oocyte aging, and the age-related decline of this pathway likely impairs oocyte health. This knowledge may create an opportunity to develop targeted treatments to reverse or prevent physiological or chemotherapy-induced oocyte aging. On the immediate practical side, women with BRCA or similar mutations may need to be specially counselled for fertility preservation.
MeSH Terms
- Aging
- Animals
- Ataxia Telangiectasia
- BRCA1 Protein
- BRCA2 Protein
- DNA Breaks, Double-Stranded
- DNA Repair
- Female
- Fertility
- Fertility Preservation
- Humans
- Mice
- Oocytes
- Ovarian Follicle
- Ovarian Reserve
- Ovary
Keywords
BRCA
BRCA1/2
- DNA repair
- anti-Mullerian hormone
- chemotherapy
- mutations
- oocyte
- ovarian aging
- ovarian reserve
- ovarian response
HIV infection leads to a phenomenon of inflammaging, in which chronic inflammation induces an immune aged phenotype, even in individuals on combined antiretroviral therapy (cART) with undetectable viremia. In this study, we investigated T cell homeostasis and telomeric DNA damage and repair machineries in cART-controlled HIV patients at risk for inflammaging. We found a significant depletion of CD4 T cells, which was inversely correlated with the cell apoptosis in virus-suppressed HIV subjects compared to age-matched healthy subjects (HS). In addition, HIV CD4 T cells were prone to DNA damage that extended to chromosome ends-telomeres, leading to accelerated telomere erosion-a hallmark of cell senescence. Mechanistically, the DNA double-strand break (DSB) sensors MRE11, RAD50, and NBS1 (MRN complex) remained intact, but both expression and activity of the DNA damage checkpoint kinase ataxia-telangiectasia mutated (ATM) and its downstream checkpoint kinase 2 (CHK2) were significantly suppressed in HIV CD4 T cells. Consistently, ATM/CHK2 activation, DNA repair, and cellular functions were also impaired in healthy CD4 T cells following ATM knockdown or exposure to the ATM inhibitor KU60019 [i]in vitro[/i], recapitulating the biological effects observed in HIV-derived CD4 T cells [i]in vivo[/i]. Importantly, ectopic expression of ATM was essential and sufficient to reduce the DNA damage, apoptosis, and cellular dysfunction in HIV-derived CD4 T cells. These results demonstrate that failure of DSB repair due to ATM deficiency leads to increased DNA damage and renders CD4 T cells prone to senescence and apoptotic death, contributing to CD4 T cell depletion or dysfunction in cART-controlled, latent HIV infection.
MeSH Terms
- Anti-Retroviral Agents
- Ataxia Telangiectasia Mutated Proteins
- Cellular Senescence
- DNA Damage
- HIV Infections
- Humans
- T-Lymphocytes
- Telomere
Keywords
- ATM
- DNA damage repair
- HIV
- T cell homeostasis
- apoptosis
- immune aging
Skin is the largest organ of the body, and is prone to be affected by external environmental factors. Skin aging is caused by both genetic and environmental factors. Furthermore, aging skin tissue is known to create a permissive tissue microenvironment that promotes the initiation, progression and resistance of cancer cells by promoting the senescence-associated secretory phenotype (SASP). Therefore, more attention should be paid to skin aging. In this review, we highlight the common Rel proteins and two activation pathways: the canonical activation pathway and the non-canonical activation pathway. Furthermore, we summarize the role of NF-κB in skin aging. The effects of UV on the skin results from the production of ROS. Excessive free radicals activate the NF-κB signaling pathway and MAPK signaling pathway, contributing to the activation of AP-1 and NF-κB. Then it increased the level of TNF-α and the expression of MMPs, which induce the degradation of ECM and accelerated skin aging. We also summarize some reported natural antioxidants and synthetic antioxidants which are related to NF-κB signals. On the other hand, NF-κB plays a key role in SASP. Upon senescence-inducing signals, ATM and ATR block p62-dependent autophagic degradation of GATA4, contributing to NF-κB activation and SASP induction.
MeSH Terms
- Animals
- Cellular Senescence
- Humans
- NF-kappa B
- Phenotype
- Signal Transduction
- Skin Aging
- Skin Neoplasms
Keywords
- NF-κB
- Senescence-associated secretory phenotype
- Skin aging
Suppressor of morphogenesis in genitalia 1 (SMG1) and ataxia telangiectasia mutated (ATM) are members of the PI3-kinase like-kinase (PIKK) family of proteins. ATM is a well-established tumour suppressor. Loss of one or both alleles of ATM results in an increased risk of cancer development, particularly haematopoietic cancer and breast cancer in both humans and mouse models. In mice, total loss of SMG1 is embryonic lethal and loss of a single allele results in an increased rate of cancer development, particularly haematopoietic cancers and lung cancer. In this study, we generated mice deficient in Atm and lacking one allele of Smg1, Atm Smg1 mice. These mice developed cancers more rapidly than either of the parental genotypes, and all cancers were haematopoietic in origin. The combined loss of Smg1 and Atm resulted in a higher level of basal DNA damage and oxidative stress in tissues than loss of either gene alone. Furthermore, Atm Smg1 mice displayed increased cytokine levels in haematopoietic tissues compared with wild-type animals indicating the development of low-level inflammation and a pro-tumour microenvironment. Overall, our data demonstrated that combined loss of Atm expression and decreased Smg1 expression increases haematopoietic cancer development.
MeSH Terms
- Animals
- Ataxia Telangiectasia Mutated Proteins
- Carcinogenesis
- Cells, Cultured
- DNA Damage
- Embryo, Mammalian
- Fibroblasts
- Gamma Rays
- Hematologic Neoplasms
- Heterozygote
- Kaplan-Meier Estimate
- Longevity
- Lymphoma
- Mice, Inbred C57BL
- Mice, Knockout
- Oxidative Stress
- Protein-Serine-Threonine Kinases
Keywords
- DNA damage
- cancer
- inflammation
- lymphoma
- oxidative stress
Ultraviolet (UV) irradiation from the sunlight is a major etiologic factor for premature skin aging. Long noncoding RNAs (lncRNAs) are involved in various biological processes, and their roles in UV irradiation-induced skin aging have recently been described. Previously, we found that the lncRNA [i]RP11-670E13.6[/i] was up-regulated and delayed cellular senescence in UVB-irradiated primary human dermal fibroblasts. Here, we performed further investigations of [i]RP11-670E13.6[/i] function. The results showed that this lncRNA directly bound to [i]miR-663a[/i] and functioned as a sponge for [i]miR-663a[/i] to modulate the derepression of Cdk4 and Cdk6, thereby delaying cellular senescence during UV irradiation-induced skin photoaging. Moreover, we found that [i]RP11-670E13.6[/i] may facilitate DNA damage repair by increasing ATM and γH2A.X levels. In addition, heterogeneous nuclear ribonucleoprotein H physically interacted with [i]RP11-670E13.6[/i] and blocked its expression. Collectively, our results suggested that the [i]RP11-670E13.6/miR-663a[/i]/[i]CDK4[/i] and [i]RP11-670E13.6/miR-663a[/i]/[i]CDK6[/i] axis, which may function as competitive endogenous RNA networks, played important roles in UVB-induced cellular senescence.
MeSH Terms
- Cell Proliferation
- Cellular Senescence
- Fibroblasts
- Heterogeneous-Nuclear Ribonucleoprotein Group F-H
- Humans
- MicroRNAs
- RNA, Long Noncoding
- Skin
- Skin Aging
- Ultraviolet Rays
Keywords
- cellular senescence
- dermal fibroblast
- lncRNA
- microRNA
- ultraviolet B
DNA damage responses are crucial for plant growth under genotoxic stress. Accumulating evidence indicates that DNA damage responses differ between plant cell types. Here, quantitative shotgun phosphoproteomics provided high-throughput analysis of the DNA damage response network in callus cells. MS analysis revealed a wide network of highly dynamic changes in the phosphoprotein profile of genotoxin-treated cells, largely mediated by the ATAXIA TELANGIECTASIA MUTATED (ATM) protein kinase, representing candidate factors that modulate plant growth, development and DNA repair. A C-terminal dual serine target motif unique to H2AX in the plant lineage showed 171-fold phosphorylation that was absent in atm mutant lines. The physiological significance of post-translational DNA damage signalling to plant growth and survival was demonstrated using reverse genetics and complementation studies of h2ax mutants, establishing the functional role of ATM-mediated histone modification in plant growth under genotoxic stress. Our findings demonstrate the complexity and functional significance of post-translational DNA damage signalling responses in plants and establish the requirement of H2AX phosphorylation for plant survival under genotoxic stress.
MeSH Terms
- ATP-Binding Cassette Transporters
- Aging
- Arabidopsis
- Arabidopsis Proteins
- Cells, Cultured
- DNA Damage
- DNA Repair
- Gene Expression Regulation, Plant
- Gene Ontology
- Germination
- Histones
- Mass Spectrometry
- Phosphorylation
- Proteome
- Seeds
- Serine
- Signal Transduction
- Stress, Physiological
- X-Rays
Keywords
- ATAXIA TELANGIECTASIA MUTATED (ATM)
- DNA damage response
- DNA repair
- phosphorylation
- seed
Telomeres progressively shorten at every round of DNA replication in the absence of telomerase. When they become critically short, telomeres trigger replicative senescence by activating a DNA damage response that is governed by the Mec1/ATR and Tel1/ATM protein kinases. While Mec1/ATR is known to block cell division when extended single-stranded DNA (ssDNA) accumulates at eroded telomeres, the molecular mechanism by which Tel1/ATM promotes senescence is still unclear. By characterizing a Tel1-hy184 mutant variant that compensates for the lack of Mec1 functions, we provide evidence that Tel1 promotes senescence by signaling to a Rad9-dependent checkpoint. Tel1-hy184 anticipates senescence onset in telomerase-negative cells, while the lack of Tel1 or the expression of a kinase-defective (kd) Tel1 variant delays it. Both Tel1-hy184 and Tel1-kd do not alter ssDNA generation at telomeric DNA ends. Furthermore, Rad9 and (only partially) Mec1 are responsible for the precocious senescence promoted by Tel1-hy184. This precocious senescence is mainly caused by the F1751I, D1985N, and E2133K amino acid substitutions, which are located in the FRAP-ATM-TRAPP domain of Tel1 and also increase Tel1 binding to DNA ends. Altogether, these results indicate that Tel1 induces replicative senescence by directly signaling dysfunctional telomeres to the checkpoint machinery.
MeSH Terms
- Amino Acid Substitution
- Ataxia Telangiectasia Mutated Proteins
- Cell Cycle Checkpoints
- Cell Division
- Cellular Senescence
- DNA Damage
- DNA Replication
- DNA, Single-Stranded
- DNA-Binding Proteins
- Intracellular Signaling Peptides and Proteins
- Mutant Proteins
- Protein-Serine-Threonine Kinases
- Saccharomyces cerevisiae
- Saccharomyces cerevisiae Proteins
- Telomerase
- Telomere
- Telomere Shortening
Keywords
- Tel1
- checkpoint
- replicative senescence
- telomere
Curcumin, a phytochemical present in the spice named turmeric, and one of the promising anti-aging factors, is itself able to induce cellular senescence. We have recently shown that cells building the vasculature senesced as a result of curcumin treatment. Curcumin-induced senescence was DNA damage-independent; however, activation of ATM was observed. Moreover, neither increased ROS production, nor even ATM were indispensable for senescence progression. In this paper we tried to elucidate the mechanism of curcumin-induced senescence. We analyzed the time-dependence of the level and activity of numerous proteins involved in senescence progression in vascular smooth muscle cells and how inhibition p38 or p38 together with ATM, two proteins involved in canonical signaling pathways, influenced cell senescence. We showed that curcumin was able to influence many signaling pathways of which probably none was dominant and sufficient to induce senescence by itself. However, we cannot exclude that the switch between initiation and progression of senescence is the result of the impact of curcumin on signaling pathways engaging AMPK, ATM, sirtuin 1 and p300 and on their reciprocal interplay. Cytostatic concentration of curcumin induced cellular stress, which exceeded the adaptive response and, in consequence, led to cellular senescence, which is triggered by time dependent activation of several signaling pathways playing diverse roles in different phases of senescence progression. We also showed that activity of β-glucuronidase, the enzyme involved in deconjugation of the main metabolites of curcumin, glucuronides, increased in senescent cells. It suggests a possible local elevation of curcumin concentration in the organism.
MeSH Terms
- Ataxia Telangiectasia Mutated Proteins
- Cellular Senescence
- Curcumin
- Down-Regulation
- Gene Silencing
- Glucuronidase
- Humans
- Muscle, Smooth, Vascular
- Signal Transduction
- p38 Mitogen-Activated Protein Kinases
Keywords
- AMPK
- ATM
- Curcumin
- Senescence
- VSMCs
- β-glucuronidase
Mesenchymal stem cells (MSCs) are attracting increasing interest for cell-based therapies, making use of both their immuno-modulating and regenerative potential. For such therapeutic applications, a massive in vitro expansion of donor cells is usually necessary to furnish sufficient material for transplantation. It is not established to what extent the long-term genomic stability and potency of MSCs can be compromised as a result of this rapid ex vivo expansion. In this study, we investigated the DNA damage response and chromosomal stability (indicated by micronuclei induction) after sub-lethal doses of gamma irradiation in murine MSCs at different stages of their in vitro expansion. Bone-marrow-derived tri-potent MSCs were explanted from 3-month-old female FVB/N mice and expanded in vitro for up to 12 weeks. DNA damage response and repair kinetics after gamma irradiation were quantified by the induction of γH2AX/53BP1 DSB repair foci. Micronuclei were counted in post-mitotic, binucleated cells using an automated image analyzer Metafer4. Involvement of DNA damage response pathways was tested using chemical ATM and DNA-PK inhibitors. Murine bone-marrow-derived MSCs in long-term expansion culture gradually lose their ability to recognize endogenous and radiation-induced DNA double-strand breaks. This impaired DNA damage response, indicated by a decrease in the number of γH2AX/53BP1 DSB repair foci, was associated with reduced ATM dependency of foci formation, a slower DNA repair kinetics, and an increased number of residual DNA double-strand breaks 7 h post irradiation. In parallel with this impaired efficiency of DNA break recognition and repair in older MSCs, chromosomal instability after mitosis increased significantly as shown by a higher number of micronuclei, both spontaneously and induced by γ-irradiation. Multifactorial regression analysis demonstrates that in vitro aging reduced DNA damage recognition in MSCs after irradiation by a multiplicative interaction with dose (p < 0.0001), whereas the increased frequency of micronuclei was caused by an additive interaction between in vitro aging and radiation dose. The detrimental impact of long-term in vitro expansion on DNA damage response of MSCs warrants a regular monitoring of this process during the ex vivo growth of these cells to improve therapeutic safety and efficiency.
MeSH Terms
- Animals
- Ataxia Telangiectasia Mutated Proteins
- Cell Nucleus
- Cells, Cultured
- Cytochalasin B
- DNA Breaks, Double-Stranded
- DNA Repair
- Female
- Gamma Rays
- Histones
- Mesenchymal Stem Cells
- Mice
- Time Factors
- Tumor Suppressor p53-Binding Protein 1
Keywords
- Adult stem cells
- DNA repair
- Genetic instability
- In vitro aging
- Ionizing radiation
- Mesenchymal stem cells
- Micronuclei
Longevity is mainly conditioned by genetic, epigenetic and environmental factors. Different genetic modifications seem to be positively associated to longevity, including SNPs in SIRT1, APOE, FOXO3A, ACE, ATM, NOS1 and NOS2 gene. Epigenetic changes as DNA hyper- and hypo-methylation influence significantly human longevity by activating/deactivating different genes involved in physiological mechanisms. Several studies have confirmed that centenarians have a lower DNA methylation content compared to young subjects, which showed more homogeneously methylated DNA region. Also the up-regulation of miR-21 seems to be more associated with longevity in different populations of long-lived subjects, suggesting its role as potential epigenetic biomarkers. A non-pharmacological treatment that seems to contrast age-related diseases and promote longevity is represented by dietary intervention. It has been evaluated the effects of dietary restriction of both single nutrients or total calories to extend lifespan. However, in daily practice it is very difficult to guarantee adherence/compliance of the subjects to dietary restriction and at the same time avoid dangerous nutritional deficiencies. As consequence, the attention has focused on a variety of substances both drugs and natural compounds able to mime the beneficial effects of caloric restriction, including resveratrol, quercetin, rapamycin, metformin and 2-deoxy-D-glucose.
MeSH Terms
- Diet Therapy
- Epigenomics
- Genetic Background
- Hormesis
- Humans
- Longevity
- Signal Transduction
Keywords
- Calorie restriction mimetic
- Dietary restriction
- Epigenetic mechanism
- Genetic modification
- Longevity
- Longevity molecular biomarkers
The binding of DNA-dependent protein kinase catalytic subunit (DNA-PKcs, also known as PRKDC) to Ku proteins at DNA double-strand breaks (DSBs) has long been considered essential for non-homologous end joining (NHEJ) repair, providing a rationale for use of DNA-PKcs inhibitors as cancer therapeutics. Given lagging clinical translation, we reexamined mechanisms and observed instead that DSB repair can proceed independently of DNA-PKcs. While repair of radiation-induced DSBs was blocked in cells expressing shRNAs targeting Ku proteins or other NHEJ core factors, DSBs were repaired on schedule despite targeting DNA-PKcs. Although we failed to observe a DSB repair defect, the γH2AX foci that formed at sites of DNA damage persisted indefinitely after irradiation, leading to cytokinesis failure and accumulation of binucleated cells. Following this mitotic slippage, cells with decreased DNA-PKcs underwent accelerated cellular senescence. We identified downregulation of ataxia-telangiectasia mutated kinase (ATM) as the critical role of DNA-PKcs in recovery from DNA damage, insofar as targeting ATM restored γH2AX foci resolution and cytokinesis. Considering the lack of direct impact on DSB repair and emerging links between senescence and resistance to cancer therapy, these results suggest reassessing DNA-PKcs as a target for cancer treatment.
MeSH Terms
- Animals
- Ataxia Telangiectasia Mutated Proteins
- Aurora Kinase B
- Cell Cycle Checkpoints
- Cell Cycle Proteins
- Cell Death
- Cellular Senescence
- Cyclin-Dependent Kinase Inhibitor p21
- Cytokinesis
- Cytoprotection
- DNA Breaks, Double-Stranded
- DNA Repair
- DNA-Activated Protein Kinase
- Down-Regulation
- Histones
- Humans
- MCF-7 Cells
- Mice
- Mitosis
- Morpholines
- Protein Kinase Inhibitors
- Protein-Serine-Threonine Kinases
- Proto-Oncogene Proteins
- Pyrones
- Radiation Tolerance
- Radiation, Ionizing
Keywords
- ATM
- DNA damage response
- DNA-PKcs
- Mitotic slippage
- Senescence
The 14th Japan-Korea joint symposium on cancer and aging research was held at an auditorium of Saga University, Japan, May 31-Jun 2, 2018. Participants presented 31 oral and 21 poster presentations, two lectures at a luncheon seminar, plus special lectures from two Korean Emeritus Professors and founders of our joint symposia. The essential parts of the lectures are reviewed here. This Symposium was called Japan-Korea, because the host country comes first. Our symposia are organized every 18 months and the program includes keynote and plenary lectures, and oral and poster presentations. (1) Subjects related to cancer development at this symposium were: prostate cancer progression, molecules activating GSK3β, suppressing the activation of cancer stem cells, profiling human B cell receptor repertoires, and hereditary gastrointestinal cancer syndrome. (2) Subjects related to treatment were: G-quadruplex ligands for glioma stem cells, tankyrase inhibitor for colorectal cancer, and eradication of ATL. (3) Cancer prevention subjects were: physical adsorption of EGCG to cell membrane, inhibition of immune evasion of cancer cells with EGCG, and prevention with antidiabetic agents. (4) Aging subjects were life span extension with Toll-like receptor 5 vaccine and reversal of senescence with inhibitors of ATM and ROCK. (5) The results of epidemiology focused on aldehyde dehyrogenase-2 and alcohol consumption. The 14th symposium demonstrated the cutting-edge of presentations with discussion of numerous ideas by the participants.
MeSH Terms
- Aging
- Humans
- Japan
- Neoplasms
- Precision Medicine
- Republic of Korea
- Translational Medical Research
Keywords
- ATL
- EGCG
- G-quadruplex
- KRAS
- PAK4
Previously, DNA damage sensing, repairing and signaling machineries were thought to mainly suppress genomic instability in response to genotoxic stress. Emerging evidence indicates a crosstalk between DNA repair machinery and the immune system. In this chapter, we attempt to decipher the molecular choreography of how factors, including ATM, BRCA1, DNA-PK, FANCA/D2, MRE11, MUS81, NBS1, RAD51 and TREX1, of multiple DNA metabolic processes are directly or indirectly involved in suppressing cytosolic DNA sensing pathway-mediated immune signaling. We provide systematic details showing how different DDR factors' roles in modulating immune signaling are not direct, but are rather a consequence of their inherent ability to sense, repair and signal in response to DNA damage. Unexpectedly, most DDR factors negatively impact the immune system; that is, the immune system shows defective signaling if there are defects in DNA repair pathways. Thus, in addition to their known DNA repair and replication functions, DDR factors help prevent erroneous activation of immune signaling. A more precise understanding of the mechanisms by which different DDR factors function in immune signaling can be exploited to redirect the immune system for both preventing and treating autoimmunity, cellular senescence and cancer in humans.
MeSH Terms
- DNA
- DNA Damage
- DNA Repair
- Humans
- Signal Transduction
Keywords
- DDR
- Genomic instability
- Innate immunity
- MRE11
- Micronuclei
- NBS1
- RAD51
- STING
- Senescence
- cGAS
The maintenance of mitochondrial function is closely linked to the control of senescence. In our previous study, we uncovered a novel mechanism in which senescence amelioration in normal aging cells is mediated by the recovered mitochondrial function upon [i]Ataxia telangiectasia mutated[/i] (ATM) inhibition. However, it remains elusive whether this mechanism is also applicable to senescence amelioration in accelerated aging cells. In this study, we examined the role of ATM inhibition on mitochondrial function in Hutchinson-Gilford progeria syndrome (HGPS) and Werner syndrome (WS) cells. We found that ATM inhibition induced mitochondrial functional recovery accompanied by metabolic reprogramming, which has been known to be a prerequisite for senescence alleviation in normal aging cells. Indeed, the induced mitochondrial metabolic reprogramming was coupled with senescence amelioration in accelerated aging cells. Furthermore, the therapeutic effect via ATM inhibition was observed in HGPS as evidenced by reduced progerin accumulation with concomitant decrease of abnormal nuclear morphology. Taken together, our data indicate that the mitochondrial functional recovery by ATM inhibition might represent a promising strategy to ameliorate the accelerated aging phenotypes and to treat age-related disease.
MeSH Terms
- Aging
- Ataxia Telangiectasia Mutated Proteins
- Cell Nucleus Shape
- Cellular Senescence
- DNA Breaks, Double-Stranded
- Fibroblasts
- Humans
- Lamin Type A
- Mitochondria
- Models, Biological
- Progeria
Keywords
- ATM inhibition
- HGPS
- KU-60019
- WS
- mitochondrial function
Hydrogen possesses antioxidative effects and cures numerous types of ophthalmopathy, but the mechanism of hydrogen on ROS-induced retinal senescence remains elusive. In this study, retinal morphology revealed that hydrogen reduced the number and size of vitreous black deposits in Bruch's membrane in NaIO3 mice. Hydrogen also reduced ROS levels in the retina as assessed by DHE staining. Moreover, this result was consistent with the downregulation of expression of the oxidative stress hallmark OGG1. These findings suggested that hydrogen can reduce retinal oxidative stress induced by NaIO3, and this result was further verified using the antioxidant ALCAR. Mechanistic analysis revealed that hydrogen significantly inhibited the downregulation of Sirt3 expression, and this notion was confirmed using AICAR, which restores Sirt3 expression and activity. Moreover, hydrogen reduced the expression of p53, p21 and p16 and the number of blue-green precipitations in the retinas of NaIO3 mice as assessed by SA-β-gal staining. We also found that hydrogen decreased the expression of the DNA damage-related protein ATM, cyclinD1 and NF-κB but increased the expression of the DNA repair-related protein HMGB1, suggesting that hydrogen inhibits senescence in retinas of NaIO3 mice. Additionally, OCT examination revealed that hydrogen suppressed retinal high reflex formation significantly and prevented the retina from thinning. This result was supported by ERG assays that demonstrated that hydrogen prevented the reduction in a- and b-wave amplitude induced by NaIO3 in mice. Thus, our data suggest that hydrogen may inhibit retinal senescence by suppressing the downregulation of Sirt3 expression through reduced oxidative stress reactions.
MeSH Terms
- Acetylcarnitine
- Aging
- Animals
- Antioxidants
- Ataxia Telangiectasia Mutated Proteins
- Cyclin D1
- DNA Damage
- Gene Expression Regulation
- HMGB1 Protein
- Humans
- Hydrogen
- Iodates
- Mice
- Oxidative Stress
- Reactive Oxygen Species
- Retina
- Retinal Degeneration
- Sirtuin 3
Keywords
- DNA repair
- Hydrogen
- Retinal oxidative stress injury
- Senescence
- Sirt3
Aplastic anemia is the bone marrow failure condition characterized by the development of hypocellularity in both marrow and peripheral blood compartments. Anti-tumor chemotherapeutic agents often exert secondary effect on hematopoietic system leading to aplastic anemia by marrow failure. The precise mechanisms behind the marrow ablative effects of the drugs remain yet to be established. The present study holds a mechanistic approach to unveil the mystery. Aplastic anemia was generated in mice with the administration of busulfan and cyclophosphamide followed by the characterization of the disease with peripheral blood hemogram, histopathological and cytochemical examinations of bone marrow. To gain deep knowledge about the molecular mechanisms of the hematopoietic disruption, cytotoxicity assay, DNA damage measurement, apoptosis study, replicative senescence analysis, redox balance study, mitochondrial membrane potential change assessment, flowcytometric expressional analysis of p21, p53, ATM, Chk-2, Necdin, Gfi-1, c-myc, KU-80 and Sod-2 were done with marrow hematopoietic stem/ progenitor cells (HSPCs). Severe blood pancytopenia and marrow hypocellularity was found in aplastic mice. Proliferative hindrance and apoptosis of marrow cells were identified as the cause behind the hematopoietic catastrophe. The genotoxic effects of the drugs triggered chromatin damage and induced replicative senescence in aplastic HSPCs by upregulating p21 in a p53 independent manner. Moreover, accumulation of genomic insults also caused apoptotic elimination of marrow cells due to disruption of mitochondrial membrane potential by generating redox imbalance. The study established the underlying mechanisms behind hematopoietic disruption during drug induced marrow aplasia. Outcome of the study may be helpful in successful designing of therapeutic strategies for the disease concerned.
MeSH Terms
- Anemia, Aplastic
- Animals
- Apoptosis
- Busulfan
- Cell Proliferation
- Cellular Senescence
- DNA Damage
- Disease Models, Animal
- Hematopoietic Stem Cells
- Membrane Potential, Mitochondrial
- Mice
- Mitochondria
- Pancytopenia
Keywords
- Aplastic anemia
- Apoptosis
- Hematopoiesis
- Replicative senescence
- Xenobiotic insults
MYCN amplification or N-Myc overexpression is found in approximately 40% NEPC and up to 20% CRPC patients. N-Myc has been demonstrated to drive disease progression and hormonal therapeutic resistance of NEPC/CRPC. Here, we aim to identify the molecular mechanisms underlying the N-Myc-driven therapeutic resistance and provide new therapeutic targets for those N-Myc overexpressed NEPC/CRPC. N-Myc overexpressing stable cell lines for LNCaP and C4-2 were generated by lentivirus infection. ADT-induced senescence was measured by SA-β-gal staining in LNCaP cells in vitro and in LNCaP xenograft tumors in vivo. Migration, cell proliferation and colony formation assays were used to measure the cellular response after overexpressing N-Myc or perturbing the miR-421/ATM pathway. CRISPR-Cas9 was used to knock out ATM in C4-2 cells and MTS cell viability assay was used to evaluate the drug sensitivity of N-Myc overexpressing C4-2 cells in response to Enzalutamide and ATM inhibitor Ku60019 respectively or in combination. N-Myc overexpression suppressed ATM expression through upregulating miR-421 in LNCaP cells. This suppression alleviated the ADT-induced senescence in vitro and in vivo. Surprisingly, N-Myc overexpression upregulated ATM expression in C4-2 cells and this upregulation promoted migration and invasion of prostate cancer cells. Further, the N-Myc-induced ATM upregulation in C4-2 cells rendered the cells resistance to Enzalutamide, and inhibition of ATM by CRISPR-Cas9 knockout or ATM inhibitor Ku60019 re-sensitized them to Enzalutamide. N-Myc differentially regulating miR-421/ATM pathway contributes to ADT resistance and Enzalutamide resistance development respectively. Combination treatment with ATM inhibitor re-sensitizes N-Myc overexpressed CRPC cells to Enzalutamide. Our findings would offer a potential combination therapeutic strategy using ATM kinase inhibitor and Enzalutamide for the treatment of a subset of mCRPC with N-Myc overexpression that accounts for up to 20% CRPC patients.
MeSH Terms
- Animals
- Ataxia Telangiectasia Mutated Proteins
- CRISPR-Cas Systems
- Carcinoma, Neuroendocrine
- Cell Line, Tumor
- Cell Movement
- Cell Proliferation
- Cell Survival
- Drug Resistance, Neoplasm
- Humans
- Male
- Mice
- MicroRNAs
- Morpholines
- N-Myc Proto-Oncogene Protein
- Phenylthiohydantoin
- Prostatic Neoplasms, Castration-Resistant
- Protein Kinase Inhibitors
- Signal Transduction
- Thioxanthenes
- Up-Regulation
- Xenograft Model Antitumor Assays
Keywords
- ATM
- ATM inhibitor
- EZH2
- Neuroendocrine
- Senescence
Bacteria inhabiting the human gut metabolize microbiota-accessible carbohydrates (MAC) contained in plant fibers and subsequently release metabolic products. Gut bacteria produce hydrogen (H₂), which scavenges the hydroxyl radical (•OH). Because H₂ diffuses within the cell, it is hypothesized that H₂ scavenges cytoplasmic •OH (cyto •OH) and suppresses cellular senescence. However, the mechanisms of cyto •OH-induced cellular senescence and the physiological role of gut bacteria-secreted H₂ have not been elucidated. Based on the pyocyanin-stimulated cyto •OH-induced cellular senescence model, the mechanism by which cyto •OH causes cellular senescence was investigated by adding a supersaturated concentration of H₂ into the cell culture medium. Cyto •OH-generated lipid peroxide caused glutathione (GSH) and heme shortage, increased hydrogen peroxide (H₂O₂), and induced cellular senescence via the phosphorylation of ataxia telangiectasia mutated kinase serine 1981 (p-ATM )/p53 serine 15 (p-p53 )/p21 and phosphorylation of heme-regulated inhibitor (p-HRI)/phospho-eukaryotic translation initiation factor 2 subunit alpha serine 51 (p-eIF2α)/activating transcription factor 4 (ATF4)/p16 pathways. Further, H₂ suppressed increased H₂O₂ by suppressing cyto •OH-mediated lipid peroxide formation and cellular senescence induction via two pathways. H₂ produced by gut bacteria diffuses throughout the body to scavenge cyto •OH in cells. Therefore, it is highly likely that gut bacteria-produced H₂ is involved in intracellular maintenance of the redox state, thereby suppressing cellular senescence and individual aging. Hence, H₂ produced by intestinal bacteria may be involved in the suppression of aging.
MeSH Terms
- Activating Transcription Factor 4
- Cellular Senescence
- Cyclin-Dependent Kinase Inhibitor p16
- Cyclin-Dependent Kinase Inhibitor p21
- Cytoplasm
- DNA Damage
- Eukaryotic Initiation Factor-2
- Fibroblasts
- Gene Expression Regulation
- Glutathione
- Humans
- Hydrogen
- Hydrogen Peroxide
- Hydroxyl Radical
- Lipid Peroxidation
- Male
- Oxidative Stress
- Signal Transduction
Keywords
- cellular senescence
- cytoplasmic hydroxyl radical
- hydrogen
- hydrogen peroxide
- lipid peroxide
Multiple myeloma (MM) is a hematological malignancy that lacks a cure. However, novel combination therapy is a current anti-MM strategy. Doxorubicin (DOX) is a type of anthracycline which is a first-line chemotherapeutic for treating MM and induces senescence in many types of cancer. Dinaciclib is a potent, small molecule CDK inhibitor with promise for treating several types of cancer in I/II phase clinical trials. In the present study the anticancer effects and underlying mechanisms of dinaciclib combined with DOX in MM RPMI-8226 cells were investigated. Results indicated that DOX induced cell viability inhibition, cell cycle arrest and senescence. Furthermore, DOX resulted in increased alterations in DNA damage-related proteins such as p-ATM, p-Chk2, p-p53, p21 and γH2AX, but not p16. Notably, the combination of dinaciclib and DOX inhibited cell growth and promoted senescence by transforming the suppressive effects of the ATM/Chk2/p53/p21 signaling pathway and enhancing the p16 signaling pathway. Thus, low-dose dinaciclib enhanced anti-MM effects mediated by DOX via transformation of p21-p16 signaling pathways, leading to accelerated senescence, but not apoptosis. The present findings suggest this approach may be a promising therapeutic strategy for the treatment of MM.
Keywords
- DNA damage
- dinaciclib
- doxorubicin
- multiple myeloma
- senescence
Women with advanced maternal age exhibit low anti-Müllerian hormone (AMH) levels and an altered follicular environment, which is associated with poor oocyte quality and embryonic developmental potential. However, the underlying mechanism is poorly understood. The present study aimed to assesswhether aging patients exhibit an activated DNA double-strandbreak (DSB) repair pathway in cumulus cells and thus, an association with poor outcomes after in vitro fertilization-embryo transfer (IVF-ET) treatment. Cumulus cells from young (≤29 y) and aging (≥37 y) human female patients were collected after oocyte retrieval. Our results indicated that aging patients showed a higher rate of γ-H2AX-positive cells than in young patients (24.33±4.55 vs.12.40±2.31, P<0.05). We also found that the mRNA expression levels of BRCA1, ATM, MRE11 and RAD51 were significantly elevated in aging cumulus cells. Accordingly, significantly increased protein levels of phospho-H2AX, BRCA1, ATM, MRE11 and RAD51 could be observed in aging cumulus cells. Moreover, aging cumulus cells showed a more frequent occurrence of early apoptosis than young cumulus cells. This study found that increases in DSBs and the activation of the repair pathway are potential indicators that may be used to predictoutcomes after IVF-ET treatment.
MeSH Terms
- Adult
- Aging
- Apoptosis
- Ataxia Telangiectasia Mutated Proteins
- Biomarkers
- Cellular Senescence
- Cumulus Cells
- DNA Breaks, Double-Stranded
- DNA Repair
- Embryo Transfer
- Female
- Fertilization in Vitro
- Histones
- Humans
- MRE11 Homologue Protein
- Prognosis
- RNA, Messenger
- Rad51 Recombinase
- Ubiquitin-Protein Ligases
Myeloid leukemia treatment is quite successful nowadays; nevertheless the development of new therapies is still necessary. In the present study, we investigated the potential of epigenetic modulators EGCG (epigallocatechin-3-gallate) and BIX-01294 (N-(1-benzylpiperidin-4-yl)-6,7-dimethoxy-2-(4-methyl-1,4-diazepan-1-yl)quinazolin-4-amine) to alter epigenetic state and cause cellular senescence in acute and chronic myeloid leukemia NB4 and K562 cells. We have shown that after leukemia cell treatment with EGCG and BIX-01294 the proliferation and survival were inhibited of both cell lines; however, only NB4 cells underwent apoptosis. Both epigenetic modulators caused cell cycle arrest in G0/G1 phase as assessed by RT-qPCR (p53, p21, Rb) and flow cytometry analysis. Increased levels of ATM, HMGA2, phosphorylated ATM, and SA-β-galactosidase staining indicated that EGCG caused cellular senescence, whereas BIX-01294 did not. Immunoblot analysis of epigenetic players DNMT1, HP1α, H3K9me3, EZH2, and SUZ12 demonstrated beneficial epigenetic modulation by both agents with exception of mainly no epigenetic changes caused in K562 cells by EGCG. Therefore, we suggest EGCG as a promising epigenetic modulator for acute promyelocytic leukemia therapy and as a potential cellular senescence inducer in both acute and chronic myeloid leukemia treatment, whereas BIX-01294 could be beneficial as an epigenetic modifier for both myeloid leukemias treatment.
MeSH Terms
- Antineoplastic Agents
- Azepines
- Catechin
- Cellular Senescence
- Drug Screening Assays, Antitumor
- Epigenesis, Genetic
- G1 Phase Cell Cycle Checkpoints
- Gene Expression Regulation, Neoplastic
- Humans
- K562 Cells
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive
- Leukemia, Promyelocytic, Acute
- Quinazolines
Keywords
- BIX-01294
- EGCG
- Epigenetic regulation
- Myeloid leukemia
- Senescence
The tumor suppressor F-box protein 31 (FBXO31) is indispensable for maintaining genomic stability. Its levels drastically increase following DNA damage, leading to cyclin D1 and MDM2 degradation and G and G /M arrest. Prolonged arrest in these phases leads to cellular senescence. Accordingly, FBXO31 needs to be kept at low basal levels in unstressed conditions for normal cell cycle progression during growth and development. However, the molecular mechanism maintaining these basal FBXO31 levels has remained unclear. Here, we identified the F-box family SCF-E3 ubiquitin ligase FBXO46 (SCF ) as an important proteasomal regulator of FBXO31 and found that FBXO46 helps maintain basal FBXO31 levels under unstressed conditions and thereby prevents premature senescence. Using molecular docking and mutational studies, we showed that FBXO46 recognizes an R[i]XX[/i]R motif located at the FBXO31 C terminus to direct its polyubiquitination and thereby proteasomal degradation. Furthermore, FBXO46 depletion enhanced the basal levels of FBXO31, resulting in senescence induction. In response to genotoxic stress, ATM (ataxia telangiectasia-mutated) Ser/Thr kinase-mediated phosphorylation of FBXO31 at Ser-278 maintained FBXO31 levels. In contrast, activated ATM phosphorylated FBXO46 at Ser-21/Ser-67, leading to its degradation via FBXO31. Thus, ATM-catalyzed phosphorylation after DNA damage governs FBXO31 levels and FBXO46 degradation via a negative feedback loop. Collectively, our findings reveal that FBXO46 is a crucial proteasomal regulator of FBXO31 and thereby prevents senescence in normal growth conditions. They further indicate that FBXO46-mediated regulation of FBXO31 is abrogated following genotoxic stress to promote increased FBXO31 levels for maintenance of genomic stability.
MeSH Terms
- Cellular Senescence
- F-Box Proteins
- Genomic Instability
- Humans
- Molecular Docking Simulation
- Phosphorylation
- Proteasome Endopeptidase Complex
- SKP Cullin F-Box Protein Ligases
- Tumor Suppressor Proteins
- Ubiquitination
Keywords
- ATM
- DNA damage
- E3 ubiquitin ligase
- F-box protein
- cell cycle
- flow cytometry
- post-transcriptional regulation
- post-translational modification (PTM)
- protein motif
- protein turnover
- senescence
- ubiquitin ligase
- ubiquitination
- ubiquitylation (ubiquitination)
There has been enormous recent progress in understanding how human cells respond to oxidative stress, such as that caused by exposure to ionizing radiation. We have witnessed a significant deciphering of the events that underlie how antioxidant responses counter pro-oxidant damage to key biological targets in all cellular compartments, including the genome and mitochondria. These cytoprotective responses include: 1. The basal cellular repertoire of antioxidant capabilities and its supporting cast of facilitator enzymes; and 2. The inducible phase of the antioxidant response, notably that mediated by the Nrf2 transcription factor. There has also been frenetic progress in defining how reactive electrophilic species swamp existing protective mechanisms to augment DNA damage, events that are embodied in the cellular "DNA-damage response", including cell cycle checkpoint activation and DNA repair, which occur on a time scale of hours to days, as well as the implementation of cellular responses such as apoptosis, autophagy, senescence and reprograming that extend the time period of damage sensing and response into weeks, months and years. It has become apparent that, in addition to the initial oxidative insult, cells typically undergo further waves of secondary reactive oxygen/nitrogen species generation, DNA damage and signaling and that these may reemerge long after the initial events have subsided, probably being driven, at least in part, by persisting DNA damage. These reactive oxygen/nitrogen species are an integral part of the pathological consequences of radiation exposure and may persist across multiple cell divisions. Because of the pervasive nature of oxidative stress, a cell will manifest different responses in different subcellular compartments and to different levels of stress injury. Aspects of these compartmentalized responses can involve the same proteins (such as ATM, p53 and p21) but in different functional guises, e.g., in cytoplasmic versus nuclear responses or in early- versus late-phase events. Many of these responses involve gene activation and new protein synthesis as well as a plethora of post-translational modifications of both basal and induced response proteins. It is these responses that we focus on in this review.
MeSH Terms
- Animals
- Antioxidants
- Ataxia Telangiectasia Mutated Proteins
- Carcinoma, Non-Small-Cell Lung
- Cell Physiological Phenomena
- Cyclin-Dependent Kinase Inhibitor p21
- DNA Damage
- DNA Repair
- DNA-(Apurinic or Apyrimidinic Site) Lyase
- Genomic Instability
- Humans
- Longevity
- Lung Neoplasms
- NF-E2-Related Factor 2
- Oxidative Stress
- Protein Biosynthesis
- Protein Processing, Post-Translational
- Radiation Exposure
- Radiation, Ionizing
- Reactive Oxygen Species
- Tumor Suppressor Protein p53
Replicative capacity of normal human cells decreases as telomeric sequence is lost at each division. It is believed that when a subset of chromosomes reach a critically short length, an ATM-initiated and p53-mediated transcriptional response inhibits cell growth, promoting cell senescence. In addition to loss of telomeric sequence, senescence can be induced by other stresses including ionizing radiation, oxidative damage, chemical crosslinkers like the chemotherapeutic agent cisplatin, as well as overactivation of oncogenes and tumor suppressors. Our group found that the expression of an isoform of the INhibitor of Growth 1 gene called ING1a increases approximately 10-fold as fibroblasts approach senescence and that forced expression rapidly induces a senescent phenotype in primary diploid fibroblasts, epithelial and endothelial cells that resembles replicative senescence by most physical and biochemical measures. ING1a induces these changes through strongly inhibiting endocytosis to block mitogen signaling by inducing the expression of intersectin 2, a key scaffolding protein of the endosomal pathway. This, in turn increases the expression of Rb and of p57 and p16 that serve to maintain Rb is an active, growth inhibitory state. The ING1a model is currently being used to better understand the mechanism(s) responsible for activating Rb to enforce the senescent state.
MeSH Terms
- Adaptor Proteins, Vesicular Transport
- Animals
- Cellular Senescence
- Cyclin-Dependent Kinase Inhibitor p16
- Cyclin-Dependent Kinase Inhibitor p57
- Endocytosis
- Endothelial Cells
- Epithelial Cells
- Fibroblasts
- Gene Expression Regulation
- Humans
- Inhibitor of Growth Protein 1
- Models, Biological
- Retinoblastoma Protein
- Tumor Suppressor Protein p53
Keywords
- Aging
- Cellular senescence
- Endocytosis
- Epigenetics
- ING1
Dysregulation of plasma lipids is associated with age-related cardiovascular diseases. L5, the most electronegative subfraction of chromatographically resolved low-density lipoprotein (LDL), induces endothelial dysfunction, whereas the least electronegative subfraction, L1, does not. In this study, we examined the effects of L5 on endothelial senescence and its underlying mechanisms. C57B6/J mice were intravenously injected with L5 or L1 (2 mg kg day ) from human plasma. After 4 weeks, nuclear γH2AX deposition and senescence-associated β-galactosidase staining indicative of DNA damage and premature senescence, respectively, were increased in the aortic endothelium of L5-treated but not L1-treated mice. Similar to that, in Syrian hamsters with elevated serum L5 levels induced by a high-fat diet, nuclear γH2AX deposition and senescence-associated β-galactosidase staining were increased in the aortic endothelium. This phenomenon was blocked in the presence of N-acetyl-cysteine (free-radical scavenger) or caffeine (ATM blocker), as well as in lectin-like oxidized LDL receptor-1 (LOX-1) knockout mice. In cultured human aortic endothelial cells, L5 augmented mitochondrial oxygen consumption and mitochondrial free-radical production, which led to ATM activation, nuclear γH2AX deposition, Chk2 phosphorylation, and TP53 stabilization. L5 also decreased human telomerase reverse transcriptase (hTERT) protein levels and activity. Pharmacologic or genetic manipulation of the reactive oxygen species (ROS)/ATM/Chk2/TP53 pathway efficiently blocked L5-induced endothelial senescence. In conclusion, L5 may promote mitochondrial free-radical production and activate the DNA damage response to induce premature vascular endothelial senescence that leads to atherosclerosis. Novel therapeutic strategies that target L5-induced endothelial senescence may be used to prevent and treat atherosclerotic vascular disease.
MeSH Terms
- Animals
- Cells, Cultured
- Cellular Senescence
- Endothelium, Vascular
- Humans
- Injections, Intravenous
- Lipoproteins, LDL
- Mesocricetus
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mitochondria
Keywords
- DNA damage response
- atherosclerosis
- electronegative lipoproteins
- mitochondria
- premature senescence
- telomerase
DNA damage accumulates with age (Lombard et al., 2005). However, whether and how robust DNA repair machinery promotes longevity is elusive. Here, we demonstrate that ATM-centered DNA damage response (DDR) progressively declines with senescence and age, while low dose of chloroquine (CQ) activates ATM, promotes DNA damage clearance, rescues age-related metabolic shift, and prolongs replicative lifespan. Molecularly, ATM phosphorylates SIRT6 deacetylase and thus prevents MDM2-mediated ubiquitination and proteasomal degradation. Extra copies of [i]Sirt6[/i] extend lifespan in [i]Atm-/-[/i] mice, with restored metabolic homeostasis. Moreover, the treatment with CQ remarkably extends lifespan of [i]Caenorhabditis elegans[/i], but not the [i]ATM-1[/i] mutants. In a progeria mouse model with low DNA repair capacity, long-term administration of CQ ameliorates premature aging features and extends lifespan. Thus, our data highlights a pro-longevity role of ATM, for the first time establishing direct causal links between robust DNA repair machinery and longevity, and providing therapeutic strategy for progeria and age-related metabolic diseases.
MeSH Terms
- Animals
- Ataxia Telangiectasia Mutated Proteins
- Caenorhabditis elegans
- Chloroquine
- DNA Repair
- Longevity
- Mice
- Mice, Knockout
- Motor Activity
- Phosphorylation
- Progeria
- Protein Processing, Post-Translational
- Proteolysis
- Proto-Oncogene Proteins c-mdm2
- Sirtuins
Keywords
- ATM
- SIRT6
- ageing
- biochemistry
- chemical biology
- chromosomes
- gene expression
- genome stability
- mouse
Ataxia-Telangiectasia (A-T) syndrome is an autosomal recessive neurodegenerative disorder characterized by cerebellar ataxia, oculocutaneous telangiectasia, immunodeficiency, chromosome instability, radiosensitivity, and predisposition to malignancy. There is growing evidence that A-T patients suffer from pathologic inflammation that is responsible for many symptoms of this syndrome, including neurodegeneration, autoimmunity, cardiovascular disease, accelerated aging, and insulin resistance. In addition, epidemiological studies have shown A-T heterozygotes, somewhat like deficient patients, are susceptible to ionizing irradiation and have a higher risk of cancers and metabolic disorders. This review summarizes clinical and molecular findings of inflammation in A-T syndrome. Ataxia-Telangiectasia Mutated (ATM), a master regulator of the DNA damage response is the protein known to be associated with A-T and has a complex nuclear and cytoplasmic role. Loss of ATM function may induce immune deregulation and systemic inflammation.
MeSH Terms
- Animals
- Ataxia Telangiectasia
- Cellular Senescence
- DNA Damage
- Haploinsufficiency
- Humans
- Inflammation
- Oxidative Stress
- Reactive Oxygen Species
Keywords
- ATM
- Ataxia–Telangiectasia
- Inflammation
- Neurodegeneration
- Reactive oxygen species
- Senescence
High mobility group box 2 (HMGB2) is an abundant, chromatin-associated, non-histone protein involved in transcription, chromatin remodeling, and recombination. Recently, the HMGB2 gene was found to be significantly downregulated during senescence and shown to regulate the expression of senescent-associated secretory proteins. Here, we demonstrate that HMGB2 transcription is repressed by p21 during radiation-induced senescence through the ATM-p53-p21 DNA damage signaling cascade. The loss of p21 abolished the downregulation of HMGB2 caused by ionizing radiation, and the conditional induction of p21 was sufficient to repress the transcription of HMGB2. We also showed that the p21 protein binds to the HMGB2 promoter region, leading to sequestration of RNA polymerase and transcription factors E2F1, Sp1, and p300. In contrast, NF-Y, a CCAAT box-binding protein complex, is required for the expression of HMGB2, but NF-Y binding to the HMGB2 promoter was unaffected by either radiation or p21 induction. A proximity ligation assay results confirmed that the chromosome binding of E2F1 and Sp1 was inhibited by p21 induction. As HMGB2 have been shown to regulate premature senescence by IR, targeting the p21-mediated repression of HMGB2 could be a strategy to overcome the detrimental effects of radiation-induced senescence.
MeSH Terms
- Adenocarcinoma
- Adenocarcinoma of Lung
- Ataxia Telangiectasia Mutated Proteins
- Cell Line, Tumor
- Cellular Senescence
- Colorectal Neoplasms
- Cyclin-Dependent Kinase Inhibitor p21
- DNA Damage
- Down-Regulation
- Fibroblasts
- HMGB2 Protein
- HT29 Cells
- Humans
- Lung Neoplasms
- Promoter Regions, Genetic
- Radiotherapy
- Transcription, Genetic
- Tumor Suppressor Protein p53
Keywords
- HMGB2
- p21
- radiation
- senescence
- transcription repression
Accumulating evidence suggests that the senescence-messaging secretome (SMS) factors released by senescent cells play a key role in cellular senescence and physiological aging. Phenomenon of the senescence induction in human endometrium-derived mesenchymal stem cells (MESCs) in response to SMS factors has not yet been described. In present study, we examine a hypothesis whether the conditioned medium from senescent cells (CM-old) may promote premature senescence of young MESCs. In this case, we assume that SMS factors, containing in CM-old are capable to trigger senescence mechanism in a paracrine manner. A long-term cultivation MESCs in the presence of CM-old caused deceleration of cell proliferation along with emerging senescence phenotype, including increase in both the cell size and SA-β-Gal activity. The phosphorylation of p53 and MAPKAPK-2, a direct target of p38MAPK, as well as the expression of p21Cip1 and p16Ink4a were increased in CM-old treated cells with senescence developing whereas the Rb phosphorylation was diminished. The senescence progression was accompanied by both enhanced ROS generation and persistent activation of DNA damage response, comprising protein kinase ATM, histone H2A.X, and adapter protein 53BP1. Thus, we suggest that a senescence inducing signal is transmitted through p16/MAPKAPK-2/Rb and DDR-mediated p53/p21/Rb signaling pathways. This study is the first to demonstrate that the SMS factors secreted in conditioned medium of senescent MESCs trigger a paracrine mechanism of premature senescence in young cells.
MeSH Terms
- Cell Communication
- Cell Line
- Cellular Senescence
- Endometrium
- Female
- Humans
- Mesenchymal Stem Cells
- Proteome
- Signal Transduction
Keywords
- DNA damage response
- Mesenchymal stem cells
- SASP
- Senescence propagation
- Signaling pathway
- Stress-induced senescence
Experimental and/or epidemiological studies suggest that prenatal exposure to bisphenol A (BPA) may delay fetal lung development and maturation and increase the susceptibility to childhood respiratory disease. However, the underlying mechanisms remain to be elucidated. In our previous study with cultured human fetal lung fibroblasts (HFLF), we demonstrated that 24-h exposure to 1 and 100 µM BPA increased GPR30 protein in the nuclear fraction. Exposure to 100 μM BPA had no effects on cell viability, but increased cytoplasmic expression of ERβ and release of GDF-15, as well as decreased release of IL-6, ET-1, and IP-10 through suppression of NFκB phosphorylation. By performing global gene expression and pathway analysis in this study, we identified molecular pathways, gene networks, and key molecules that were affected by 100, but not 0.01 and 1 µM BPA in HFLF. Using multiple genomic and proteomic tools, we confirmed these changes at both gene and protein levels. Our data suggest that 100 μM BPA increased CYP1B1 and HSD17B14 gene and protein expression and release of endogenous estradiol, which was associated with increased ROS production and DNA double-strand breaks, upregulation of genes and/or proteins in steroid synthesis and metabolism, and activation of Nrf2-regulated stress response pathways. In addition, BPA activated ATM-p53 signaling pathway, resulting in increased cell cycle arrest at G1 phase, senescence and autophagy, and decreased cell proliferation in HFLF. The results suggest that prenatal exposure to BPA at certain concentrations may affect fetal lung development and maturation, and thereby affecting susceptibility to childhood respiratory diseases.
MeSH Terms
- 17-Hydroxysteroid Dehydrogenases
- Air Pollutants, Occupational
- Autophagy
- Benzhydryl Compounds
- Cell Cycle Checkpoints
- Cellular Senescence
- Cytochrome P-450 CYP1B1
- Estradiol
- Fibroblasts
- Humans
- Lung
- NF-E2-Related Factor 2
- Phenols
- Reactive Oxygen Species
- Tumor Suppressor Protein p53
- Up-Regulation
Keywords
- ATM signaling
- Autophagy
- Bisphenol A
- CYP1B1
- Cell cycle arrest
- DNA double-strand breaks
- Estradiol release
- G1/S transition
- HSD17B14
- Human fetal lung fibroblasts
- Nrf2
- ROS
- Senescence
- Steroid synthesis and metabolism
- p53
- γ-H2AX
Biological aging is a complex process dependent on the interplay of cell autonomous and tissue contextual changes which occur in response to cumulative molecular stress and manifest through adaptive transcriptional reprogramming. Here we describe a transcription factor (TF) meta-analysis of gene expression datasets accrued from 18 tissue sites collected at different biological ages and from 7 different in-vitro aging models. In-vitro aging platforms included replicative senescence and an energy restriction model in quiescence (ERiQ), in which ATP was transiently reduced. TF motifs in promoter regions of trimmed sets of target genes were scanned using JASPAR and TRANSFAC. TF signatures established a global mapping of agglomerating motifs with distinct clusters when ranked hierarchically. Remarkably, the ERiQ profile was shared with the majority of in-vivo aged tissues. Fitting motifs in a minimalistic protein-protein network allowed to probe for connectivity to distinct stress sensors. The DNA damage sensors ATM and ATR linked to the subnetwork associated with senescence. By contrast, the energy sensors PTEN and AMPK connected to the nodes in the ERiQ subnetwork. These data suggest that metabolic dysfunction may be linked to transcriptional patterns characteristic of many aged tissues and distinct from cumulative DNA damage associated with senescence.
MeSH Terms
- Aging
- Cluster Analysis
- Humans
- Promoter Regions, Genetic
- Protein Binding
- Transcription Factors
The ataxia-telangiectasia mutated (ATM) protein kinase has been extensively studied for its role in the DNA damage response and its association with the disease ataxia telangiectasia. There is increasing evidence that ATM also plays an important role in other cellular processes, including carbon metabolism. Carbon metabolism is highly dysregulated in cancer due to the increased need for cellular biomass. A number of recent studies report a non-canonical role for ATM in the regulation of carbon metabolism. This review highlights what is currently known about ATM's regulation of carbon metabolism, the implication of these pathways in cancer, and the development of ATM inhibitors as therapeutic strategies for cancer.
Keywords
- AKT
- ataxia-telangiectasia mutated
- c-myc
- cancer
- cellular metabolism
- p53
- reactive oxygen species
- senescence
The aging process is the major driver of morbidity and mortality, steeply increasing the risk to succumb to cancer, cardiovascular disease, infection and neurodegeneration. Inflammation is a common denominator in age-related pathologies, identifying the immune system as a gatekeeper in aging overall. Among immune cells, T cells are long-lived and exposed to intense replication pressure, making them sensitive to aging-related abnormalities. In successful T cell aging, numbers of naïve cells, repertoire diversity and activation thresholds are preserved as long as possible; in maladaptive T cell aging, protective T cell functions decline and pro-inflammatory effector cells are enriched. Here, we review in the model system of rheumatoid arthritis (RA) how maladaptive T cell aging renders the host susceptible to chronic, tissue-damaging inflammation. In T cells from RA patients, known to be about 20years pre-aged, three interconnected functional domains are altered: DNA damage repair, metabolic activity generating energy and biosynthetic precursor molecules, and shaping of plasma membranes to promote T cell motility. In each of these domains, key molecules and pathways have now been identified, including the glycolytic enzymes PFKFB3 and G6PD; the DNA repair molecules ATM, DNA-PKcs and MRE11A; and the podosome marker protein TKS5. Some of these molecules may help in defining targetable pathways to slow the T cell aging process.
MeSH Terms
- Aging
- Arthritis, Rheumatoid
- Ataxia Telangiectasia Mutated Proteins
- Calcium-Binding Proteins
- DNA Damage
- DNA Repair
- Humans
- Inflammation
- MRE11 Homologue Protein
- T-Lymphocytes
- Telomere Shortening
Keywords
- ATM
- DNA damage responses
- DNA-PKcs
- Inflammation
- MRE11A
- Rheumatoid arthritis
- T cell aging
- Telomere
- mtDNA
Senescence is a terminal differentiation program that halts the growth of damaged cells and must be circumvented for cancer to arise. Here we describe a panel of genetic screens to identify genes required for replicative senescence. We uncover a role in senescence for the potent tumor suppressor and ATM substrate USP28. USP28 controls activation of both the TP53 branch and the GATA4/NFkB branch that controls the senescence-associated secretory phenotype (SASP). These results suggest a role for ubiquitination in senescence and imply a common node downstream from ATM that links the TP53 and GATA4 branches of the senescence response.
MeSH Terms
- Ataxia Telangiectasia Mutated Proteins
- Cellular Senescence
- GATA4 Transcription Factor
- Gene Expression Regulation
- Gene Library
- HCT116 Cells
- Humans
- Reproducibility of Results
- Tumor Suppressor Protein p53
- Ubiquitin Thiolesterase
- Ubiquitination
Keywords
- GATA4
- USP28
- senescence
Mantle cell lymphoma (MCL) is a B-cell hemopathy characterized by the t(11;14) translocation and the aberrant overexpression of cyclin D1. This results in an unrestrained cell proliferation. Other genetic alterations are common in MCL cells such as SOX11 expression, mutations of ATM and/or TP53 genes, activation of the NF-κB signaling pathway and NOTCH receptors. These alterations lead to the deregulation of the apoptotic machinery and resistance to drugs. We observed that among a panel of MCL cell lines, REC1 cells were resistant towards genotoxic stress. We studied the molecular basis of this resistance. We analyzed the cell response regarding apoptosis, senescence, cell cycle arrest, DNA damage response and finally the 26S proteasome activity following a genotoxic treatment that causes double strand DNA breaks. MCL cell lines displayed various sensitivity/resistance towards genotoxic stress and, in particular, REC1 cells did not enter apoptosis or senescence after an etoposide treatment. Moreover, the G2/M cell cycle checkpoint was deficient in REC1 cells. We observed that three main actors of apoptosis, senescence and cell cycle regulation (cyclin D1, MCL1 and CDC25A) failed to be degraded by the proteasome machinery in REC1 cells. We ruled out a default of the βTrCP E3-ubiquitine ligase but detected a lowered 26S proteasome activity in REC1 cells compared to other cell lines. The resistance of MCL cells to genotoxic stress correlates with a low 26S proteasome activity. This could represent a relevant biomarker for a subtype of MCL patients with a poor response to therapies and a high risk of relapse.
MeSH Terms
- Antineoplastic Agents, Phytogenic
- Apoptosis
- Cell Line, Tumor
- DNA Breaks, Double-Stranded
- DNA Repair
- DNA, Neoplasm
- Drug Resistance, Neoplasm
- Etoposide
- Gene Expression Regulation, Neoplastic
- Humans
- Lymphoma, Mantle-Cell
- Proteasome Endopeptidase Complex
Keywords
- 26S proteasome
- Apoptosis
- B-cell lymphoma
- Cell cycle
- DNA repair
- Double-strand break
- PSMB6
- Resistance/sensitivity
- Senescence
- Ubiquitin ligase
Cell senescence is involved in the process of organ damage and repair; however, the underlying molecular mechanism needs to be further explored. Senescence-related genes (ie, p21, p53, and ataxia telangiectasia mutated [[[ATM]]]) were shown to be elevated after myocardial infarction (MI) in both mouse and human hearts. Ten- to 12-week-old male wild-type littermates (ATM ) and ATM heterozygous mice (ATM ) were subjected to MI. Cardiac echography showed that ATM haplodeficiency did not affect the survival rate but aggravated heart failure at day 28 post MI. Histologic analysis showed increased fibrosis in the noninfarct area of ATM mice compared with that in ATM mice. Senescence-associated β-galactosidase staining showed that the number of senescent fibroblasts was decreased when ATM was haplodeficient both in vivo and in vitro. Costaining of α-smooth muscle actin with p53 or p19 showed fewer senescent myofibroblasts in ATM mouse hearts. Moreover, angiogenesis was also examined using the endothelial markers CD31 both at early (day 7) and late stages (day 28) after MI, and ATM haplodeficiency reduced angiogenesis after MI. Finally, cardiac fibroblasts were isolated from infarcted mouse heart and the medium were tested for its capacity of endothelial tubing formation, revealing that ATM haplodeficiency led to lower vascular endothelial growth factor production from cardiac fibroblast and reduced capacity of endothelial tube formation in vitro. The present study shows that ATM haplodeficiency decreases fibroblast senescence and vascular endothelial growth factor production and impaired angiogenesis in response to MI, leading to accelerated heart failure.
MeSH Terms
- Actins
- Animals
- Ataxia Telangiectasia Mutated Proteins
- Cellular Senescence
- Cyclin-Dependent Kinase Inhibitor p19
- Disease Models, Animal
- Disease Progression
- Fibrosis
- Genetic Predisposition to Disease
- Haploinsufficiency
- Heart Failure
- Male
- Mice, Inbred C57BL
- Mice, Knockout
- Myocardial Infarction
- Myocardium
- Myofibroblasts
- Neovascularization, Physiologic
- Phenotype
- Platelet Endothelial Cell Adhesion Molecule-1
- Signal Transduction
- Time Factors
- Tumor Suppressor Protein p53
- Vascular Endothelial Growth Factor A
- Ventricular Function, Left
- Ventricular Remodeling
Keywords
- angiogenesis
- fibroblasts
- myocardial infarction
- senescence
- vascular endothelial growth factor
The number of oocytes obtained from lambs after FSH treatment is far greater than those acquired from adult ewes. However, these oocytes typically have reduced viability in comparison with adult ewe oocytes. However, the molecular mechanisms of differences in viability between lamb and ewe oocytes remain unknown. In the present research, we applied iTRAQ coupled with LC-MS/MS proteomic analysis in order to investigate the proteomic expression profile of granulosa cells from lambs and ewes following stimulation with FSH. We detected 5649 proteins; 574 were differentially expressed between adults and juveniles. Based on Gene Ontology enrichment and KEGG pathway analysis, the majority of DEPs are participated in metabolic processes, ribosome and MAPK signaling pathways. Expression levels in ewes turned out to be lower than lambs. Protein interaction network analysis generated by STRING identified MAPK1, SMAD2, SMAD4, CDK1, FOS and ATM as the major findings among 54 significant differentially expressed of proteins. Quantitative real-time PCR analysis was applied to verify the proteomic analysis. These proteins which were identified in lambs may contribute to the reduction of oocyte quality compared to adults. The present research provides understanding of the molecular mechanism for follicle development in lambs.
MeSH Terms
- Aging
- Animals
- Embryo Transfer
- Female
- Fertility
- Fertilization in Vitro
- Follicle Stimulating Hormone
- Granulosa Cells
- Oocytes
- Proteomics
- Real-Time Polymerase Chain Reaction
- Sexual Maturation
- Sheep, Domestic
- Transcriptome
Keywords
- Granulosa cells
- Lamb
- Proteomics
- iTRAQ
To identify the role of DNA double-strain damage repairing pathway in the development of diabetics atherosclerosis. Wistar male rats were randomly divided into three groups: control group (group A), balloon injury group (group B) and diabetes balloon injury group (group C). Streptozotocin (STZ) was injected into rat abdomen to induce diabetes. After stabilizing high glucose, rats in group B and group C were both under aortic balloon injury technique and fed high lipid forage post-operatively. Glucose levels and weight were observed weekly. Segments of aortoa of three groups were taken at 2, 4, 6 and 8 weeks, staining of senescent β-galactosidase (SA-β-gal) staining, HE and changes of aorta under light microscope were observed. The area of tunica intima (I) and tunica media (M) in aorta was measured, and their ratio (I/M) were analyzed. Expressions of gamma-histong family 2A variant (γ-H2AX), phosphorylated ataxia telangiectasia mutated (ATM), phosphorylated checkpoint kinasen 2 (CHK2) and phosphorylated P53 were detected by immunohistochemical staining. SA-β-gal staining positive areas were dotted around in group B and group C [CM(155.3mm]but not in group A at two At the same a slight hyperlasia of aortic neointima was observed in HE staining of group B and group C. SA-β-gal staining was positive scattered within the tunica intima of aorta of group B and group C at four weeks, and HE staining promted a significantly greater of aortic neointima in the group C than that in the other two group ([i]P[/i]<0.05). Positive regions of SA-β-gal staining were more in group C than group B at six weeks. Typical atherosclerotic plaques were formed, vascular smooth muscle cells were disordered arranged and foam cells were aggregated in the plaques of group C at six weeks post-operatively, and intimal membrane areas increased than group A and group B ([i]P[/i] <0.05). At 8 weeks, SA-β-gal positive areas in group C were greater than in group B. The arteriolar wall was markedly thickened and the lumen was narrowed. The area of intimal membrane and the I/M radio were significantly greater in group C than those in group A and group B ([i]P[/i] <0.05). Positive expressed of γ-H2AX, phosphorylated ATM, phosphorylated CHK2 and phosphorylated P53 were observed in typical atherosclerotic foci of group C, and weaker expressed in group B. Cellular senescence of vascular edothelium is triggered and DNA double-strain damage is increased in diabetes. The DNA double-strain damage repairing machines may participate in the development of diabetic atherosclerosis.
MeSH Terms
- Animals
- Ataxia Telangiectasia Mutated Proteins
- Atherosclerosis
- Checkpoint Kinase 2
- DNA Damage
- DNA Repair
- Diabetes Mellitus, Experimental
- Histones
- Male
- Random Allocation
- Rats
- Rats, Wistar
- Tumor Suppressor Protein p53
- Tunica Intima
Keywords
- Atherosclerosis
- Cellular senescence
- DNA double-strain damage repairing mechanisms
- Diabetes
Neurons are exposed to high levels of DNA damage from both physiological and pathological sources. Neurons are post-mitotic and their loss cannot be easily recovered from; to cope with DNA damage a complex pathway called the DNA damage response (DDR) has evolved. This recognizes the damage, and through kinases such as ataxia-telangiectasia mutated (ATM) recruits and activates downstream factors that mediate either apoptosis or survival. This choice between these opposing outcomes integrates many inputs primarily through a number of key cross-road proteins, including ATM, p53, and p21. Evidence of re-entry into the cell-cycle by neurons can be seen in aging and diseases such as Alzheimer's disease. This aberrant cell-cycle re-entry is lethal and can lead to the apoptotic death of the neuron. Many downstream factors of the DDR promote cell-cycle arrest in response to damage and appear to protect neurons from apoptotic death. However, neurons surviving with a persistently activated DDR show all the features known from cell senescence; including metabolic dysregulation, mitochondrial dysfunction, and the hyper-production of pro-oxidant, pro-inflammatory and matrix-remodeling factors. These cells, termed senescence-like neurons, can negatively influence the extracellular environment and may promote induction of the same phenotype in surrounding cells, as well as driving aging and age-related diseases. Recently developed interventions targeting the DDR and/or the senescent phenotype in a range of non-neuronal tissues are being reviewed as they might become of therapeutic interest in neurodegenerative diseases.
MeSH Terms
- Animals
- Apoptosis
- Ataxia Telangiectasia
- Cell Cycle
- Cellular Senescence
- DNA Damage
- Histones
- Models, Biological
- Neurons
Keywords
- Aging
- DNA damage response
- apoptosis
- cell senescence
- neurodegeneration
Senescence, defined as irreversible cell-cycle arrest, is the main driving force of aging and age-related diseases. Here, we performed high-throughput screening to identify compounds that alleviate senescence and identified the ataxia telangiectasia mutated (ATM) inhibitor KU-60019 as an effective agent. To elucidate the mechanism underlying ATM's role in senescence, we performed a yeast two-hybrid screen and found that ATM interacted with the vacuolar ATPase V subunits ATP6V1E1 and ATP6V1G1. Specifically, ATM decreased E-G dimerization through direct phosphorylation of ATP6V1G1. Attenuation of ATM activity restored the dimerization, thus consequently facilitating assembly of the V and V domains with concomitant reacidification of the lysosome. In turn, this reacidification induced the functional recovery of the lysosome/autophagy system and was coupled with mitochondrial functional recovery and metabolic reprogramming. Together, our data reveal a new mechanism through which senescence is controlled by the lysosomal-mitochondrial axis, whose function is modulated by the fine-tuning of ATM activity.
MeSH Terms
- Adenosine Triphosphatases
- Aging
- Animals
- Ataxia Telangiectasia Mutated Proteins
- Cell Nucleus
- Drug Delivery Systems
- Enzyme Activation
- Flow Cytometry
- Humans
- Hydrogen-Ion Concentration
- Lysosomes
- Mice
- Mitochondria
- Morpholines
- Phosphorylation
- Protein Kinase Inhibitors
- Reactive Oxygen Species
- Thioxanthenes
In later life, people are faced with a multitude of risky decisions that concern their health, finance, and personal security. Older adults often exercise caution in situations that involve risk. In this research, we asked whether older adults are also more responsive to warnings about potential risk. An answer to this question could reveal a factor underlying increased cautiousness in older age. In Study 1, participants decided whether they would engage in risky activities (e.g., using an ATM machine in the street) in four realistic scenarios about which participants could be expected to have relevant knowledge or experience. They then made posterior decisions after listening to audio extracts of real reports relevant to each activity. In Study 2, we explored the role that emotions play in decision updating. As in Study 1, participants made prior and posterior decisions, with the exception that for each scenario the reports were presented in their original audio format (high emotive) or in a written transcript format (low emotive). Following each posterior decision, participants indicated their emotional valence and arousal responses to the reports. In both studies, older adults engaged in fewer risky activities than younger adults, indicative of increased cautiousness in older age, and exhibited stronger decision updating in response to the reports. Older adults also showed stronger emotional responses to the reports, even though emotional responses did not differ for audio and written transcript formats. Finally, age differences in emotional responses to the reports accounted for age differences in decision updating.
Keywords
- Aging
- risk perception
- risk taking
Expansion of mesenchymal stromal/stem cells (MSCs) used in clinical practices may be associated with accumulation of genetic instability. Understanding temporal and mechanistic aspects of this process is important for improving stem cell therapy protocols. We used γH2AX foci as a marker of a genetic instability event and quantified it in MSCs that undergone various numbers of passage (3-22). We found that γH2AX foci numbers increased in cells of late passages, with a sharp increase at passage 16-18. By measuring in parallel foci of ATM phosphorylated at Ser-1981 and their co-localization with γaH2AX foci, along with differentiating cells into proliferating and resting by using a Ki67 marker, we conclude that the sharp increase in γH2AX foci numbers was ATM-independent and happened predominantly in proliferating cells. At the same time, gradual and moderate increase in γH2AX foci with passage number seen in both resting and proliferating cells may represent a slow, DNA double-strand break related component of the accumulation of genetic instability in MSCs. Our results provide important information on selecting appropriate passage numbers exceeding which would be associated with substantial risks to a patient-recipient, both with respect to therapeutic efficiency and side-effects related to potential neoplastic transformations due to genetic instability acquired by MSCs during expansion.
MeSH Terms
- Adult
- Cell Differentiation
- Cell Proliferation
- Cells, Cultured
- Genomic Instability
- Histones
- Humans
- Male
- Mesenchymal Stem Cells
- Phosphorylation
Keywords
- DNA double-strand breaks
- cellular senescence
- genome instability
- long-term cultivation
- mesenchymal stromal cells
- replicative senescence
- γH2AX foci
Intracellular calcium ([Ca ] ) has been reported to play an important role in autophagy, apoptosis and necrosis, however, a little is known about its impact in senescence. Here we investigated [Ca ] contribution to oxidative stress-induced senescence of human endometrium-derived stem cells (hMESCs). In hMESCs sublethal H O -treatment resulted in a rapid calcium release from intracellular stores mediated by the activation of PLC/IP3/IP3R pathway. Notably, further senescence development was accompanied by persistently elevated [Ca ] levels. In H O -treated hMESCs, [Ca ] chelation by BAPTA-AM (BAPTA) was sufficient to prevent the expansion of the senescence phenotype, to decrease endogenous reactive oxygen species levels, to avoid G0/G1 cell cycle arrest, and finally to retain proliferation. Particularly, loading with BAPTA attenuated phosphorylation of the main DNA damage response members, including ATM, 53BP1 and H2A.X and reduced activation of the p53/p21/Rb pathway in H O -stimulated cells. Next, we revealed that BAPTA induced an early onset of AMPK-dependent autophagy in H O -treated cells as confirmed by both the phosphorylation status of AMPK/mTORC1 pathway and the dynamics of the LC3 lipidization. Summarizing the obtained data we can assume that calcium chelation is able to trigger short-term autophagy and to prevent the premature senescence of hMESCs under oxidative stress.
MeSH Terms
- AMP-Activated Protein Kinases
- Apoptosis
- Autophagy
- Calcium
- Cellular Senescence
- Chelating Agents
- Egtazic Acid
- Endometrium
- Female
- Humans
- Hydrogen Peroxide
- Oxidants
- Oxidative Stress
- Phosphorylation
- Reactive Oxygen Species
- Signal Transduction
- Stem Cells
Keywords
- autophagy
- calcium
- endometrial stem cells
- oxidative stress
- senescence
Mutations in the ataxia-telangiectasia (A-T)-mutated ([i]ATM[/i]) gene give rise to the human genetic disorder A-T, characterized by immunodeficiency, cancer predisposition, and neurodegeneration. Whereas a series of animal models recapitulate much of the A-T phenotype, they fail to present with ataxia or neurodegeneration. We describe here the generation of an [i]Atm[/i] missense mutant [amino acid change of leucine (L) to proline (P) at position 2262 (L2262P)] rat by intracytoplasmic injection (ICSI) of mutant sperm into oocytes. [i]Atm[/i]-mutant rats ([i]Atm [/i] ) expressed low levels of ATM protein, suggesting a destabilizing effect of the mutation, and had a significantly reduced lifespan compared with [i]Atm [/i] Whereas these rats did not show cerebellar atrophy, they succumbed to hind-limb paralysis (45%), and the remainder developed tumors. Closer examination revealed the presence of both dsDNA and ssDNA in the cytoplasm of cells in the hippocampus, cerebellum, and spinal cord of [i]Atm [/i] rats. Significantly increased levels of IFN-β and IL-1β in all 3 tissues were indicative of DNA damage induction of the type 1 IFN response. This was further supported by NF-κB activation, as evidenced by p65 phosphorylation (P65) and translocation to the nucleus in the spinal cord and parahippocampus. Other evidence of neuroinflammation in the brain and spinal cord was the loss of motor neurons and the presence of increased activation of microglia. These data provide support for a proinflammatory phenotype that is manifested in the [i]Atm[/i] mutant rat as hind-limb paralysis. This mutant represents a useful model to investigate the importance of neuroinflammation in A-T.
MeSH Terms
- Amino Acid Sequence
- Animals
- Ataxia Telangiectasia
- Ataxia Telangiectasia Mutated Proteins
- Brain
- Cell Death
- Cell Nucleus
- Cytosol
- DNA
- DNA Damage
- DNA Repair
- Inflammation
- Interferon-beta
- Longevity
- Microglia
- Mutation, Missense
- NF-kappa B
- Nerve Degeneration
- Phenotype
- Protein Transport
- Rats
Keywords
- ataxia-telangiectasia
- autoinflammatory
- cGAS/STING
- innate immunity
Cellular senescence is an outcome of the accumulation of DNA damage which induces the growth arrest in cells. Physiologically, it is presumed to be mediated by accumulation of reactive oxygen species (ROS). Here, we show that another free radical, nitric oxide (NO) produced during inflammation or present as an environmental pollutant can also induce cellular senescence. In primary cells and various immortalized cell lines, exposure to chronic NO, through external addition or internally generated by iNOS expression, leads to the activation of DNA damage response and causes cellular senescence. The phenotype generated by NO includes robust growth arrest, increase in the levels of the DNA damage foci, ROS, SAβ-gal staining, and inflammatory cytokines like IL-6 and IL-8, all hallmarks of cellular senescence similar to replicative senescence. Mechanistically, inhibitor and knockdown analysis revealed that NO mediates senescence through ATM kinase activation and the viability of cells is dependent on both ROS and ATM kinase involving the ATM-ROS-iNOS axis. Overall, we demonstrate that nitric oxide mediates cellular senescence through a novel free radical dependent genotoxic stress pathway.
MeSH Terms
- A549 Cells
- Ataxia Telangiectasia Mutated Proteins
- Cell Death
- Cell Line
- Cell Survival
- Cellular Senescence
- DNA Damage
- Fibroblasts
- Gene Expression Regulation
- HeLa Cells
- Humans
- Interleukin-6
- Interleukin-8
- Nitric Oxide
- Nitric Oxide Synthase Type II
- Nitroprusside
- Reactive Oxygen Species
- Signal Transduction
Keywords
- ATM kinase
- Cellular senescence
- DNA damage response
- Free radicals
- Nitric oxide
- iNOS
Ataxia telangiectasia (A-T) is a rare autosomal recessive disease characterized by progressive neurodegeneration and cerebellar ataxia. A-T is causally linked to defects in ATM, a master regulator of the response to and repair of DNA double-strand breaks. The molecular basis of cerebellar atrophy and neurodegeneration in A-T patients is unclear. Here we report and examine the significance of increased PARylation, low NAD , and mitochondrial dysfunction in ATM-deficient neurons, mice, and worms. Treatments that replenish intracellular NAD reduce the severity of A-T neuropathology, normalize neuromuscular function, delay memory loss, and extend lifespan in both animal models. Mechanistically, treatments that increase intracellular NAD also stimulate neuronal DNA repair and improve mitochondrial quality via mitophagy. This work links two major theories on aging, DNA damage accumulation, and mitochondrial dysfunction through nuclear DNA damage-induced nuclear-mitochondrial signaling, and demonstrates that they are important pathophysiological determinants in premature aging of A-T, pointing to therapeutic interventions.
MeSH Terms
- Animals
- Ataxia Telangiectasia
- Ataxia Telangiectasia Mutated Proteins
- Behavior, Animal
- Caenorhabditis elegans
- Cells, Cultured
- DNA Repair
- Disease Models, Animal
- Gene Knockdown Techniques
- Health
- Homeostasis
- Longevity
- Metabolomics
- Mice
- Mitophagy
- NAD
- Neurons
- Phenotype
- Phthalazines
- Piperazines
- Proteomics
- Rats, Sprague-Dawley
- Signal Transduction
- Sirtuin 1
In this issue, Fang et al. (2016) show that both the DNA repair defect and mitochondrial dysfunction in ATM cells or mice are mitigated by the anti-aging compound nicotinamide riboside or a SIRT1 activator. This broad suppression by activating the NAD /SIRT1 axis may generally apply to diseases and aging maladies.
MeSH Terms
- Aging
- Animals
- Mice
- NAD
- Sirtuin 1
The ataxia telangiectasia mutated (ATM)-interacting protein ATMIN mediates noncanonical ATM signaling in response to oxidative and replicative stress conditions. Like ATM, ATMIN can function as a tumor suppressor in the hematopoietic system: deletion of Atmin under the control of CD19-Cre results in B-cell lymphomas in aging mice. ATM signaling is essential for lymphopoiesis and hematopoietic stem cell (HSC) function; however, little is known about the role of ATMIN in hematopoiesis. We thus sought to investigate whether the absence of ATMIN would affect primitive hematopoietic cells in an ATM-dependent or -independent manner. Apart from its role in B-cell development, we show that ATMIN has an ATM-independent function in the common myeloid progenitors (CMPs) by deletion of Atmin in the entire hematopoietic system using Vav-Cre. Despite the lack of lymphoma formation, ATMIN-deficient mice developed chronic leukopenia as a result of high levels of apoptosis in B cells and CMPs and induced a compensatory mechanism in which HSCs displayed enhanced cycling. Consequently, ATMIN-deficient HSCs showed impaired regeneration ability with the induction of the DNA oxidative stress response, especially when aged. ATMIN, therefore, has multiple roles in different cell types, and its absence results in perturbed hematopoiesis, especially during stress conditions and aging.
MeSH Terms
- Aging
- Animals
- Apoptosis
- Ataxia Telangiectasia Mutated Proteins
- B-Lymphocytes
- Chronic Disease
- Gene Deletion
- Hematopoiesis
- Hematopoietic Stem Cells
- Leukopenia
- Mice
- Mice, Knockout
- Oxidative Stress
- Transcription Factors
In our previous study, we demonstrated that the repair efficiency of DNA double-strand breaks declines with increasing age in rat primordial follicles. In the present study, we extended our studies to buffalo (Bubalus bubalis) wherein we studied the expression of BRCA-1 related DNA repair genes in primordial follicles of young (12 months-22 months) and adult (72-96 months) buffaloes. The relative expression of selected genes, as determined by RT-PCR, revealed a significant (p < 0.05) decrease in mRNA levels of BRCA1, MRE11, RAD51, ATM, and H2AX in adult primordial follicles as compared to the young. Western blot analysis revealed a significant (p < 0.05) decrease in the expression of phosphorylated protein levels of BRCA1 and H2AX in adult buffalo primordial follicles. The protein expression profile of young and adult buffalo primordial follicles revealed differential expression of proteins involved in mitochondrial function, cell survival and cell metabolism. Similar to reports from aging rodent and human primordial follicles, our findings support the fact that impairment of DNA repair may be an universal mechanism involved in oocyte aging.
MeSH Terms
- Aging
- Animals
- Buffaloes
- Female
- Gene Expression Regulation, Developmental
- Ovarian Follicle
- Ovary
- Proteome
- Transcriptome
Keywords
- BRCA1
- Bubalus bubalis
- DNA repair
- primordial follicles
- proteomics
- water buffalo
DNA-damage induces a DNA-damage response (DDR) in mammalian cells. The response, depending upon the cell-type and the extent of DNA-damage, ultimately results in cell death or cellular senescence. DDR-induced signaling in cells activates the ATM-p53 and ATM-IKKα/β-interferon (IFN)-β signaling pathways, thus leading to an induction of the p53 and IFN-inducible IFI16 gene. Further, upon DNA-damage, DNA accumulates in the cytoplasm, thereby inducing the IFI16 protein and STING-dependent IFN-β production and activation of the IFI16 inflammasome, resulting in the production of proinflammatory cytokines (e.g., IL-1β and IL-18). Increased expression of IFI16 protein in a variety of cell-types promotes cellular senescence. However, reduced expression of IFI16 in cells promotes cell proliferation. Because expression of the IFI16 gene is induced by activation of DNA-damage response in cells and increased levels of IFI16 protein in cells potentiate the p53-mediated transcriptional activation of genes and p53 and pRb-mediated cell cycle arrest, we discuss how an improved understanding of the role of IFI16 protein in cellular senescence and associated inflammatory secretory phenotype is likely to identify the molecular mechanisms that contribute to the development of aging-associated human inflammatory diseases and a failure to cancer therapy.
MeSH Terms
- Aging
- Cellular Senescence
- DNA Damage
- Humans
- Inflammasomes
- Nuclear Proteins
- Phosphoproteins
- Signal Transduction
- Transcriptional Activation
- Tumor Suppressor Protein p53
Keywords
- Cancer
- Cellular senescence
- DNA-damage
- IFI16
- Inflammation
- Interferon
- p53
Telomere uncapping is thought to be the fundamental cause of replicative cellular senescence, but the cellular machineries mediating this process have not been fully understood. In the present study, we present the role of Sp1 transcription factor in the state of telomere uncapping using the TRF2(ΔBΔM)-induced senescence model in human diploid fibroblasts. We observed that the expression of Sp1 is down-regulated in the TRF2(ΔBΔM)-induced senescence, which was mediated by ATM and p38 MAPK. In addition, overexpression of Sp1 prevented the TRF2(ΔBΔM)-induced senescence. Among transcriptional targets of Sp1, expression levels of nuclear transport genes such as karyopherin α, Nup107, and Nup50 were down-regulated in the TRF2(ΔBΔM)-induced senescence, which was prevented by Sp1 overexpression. Moreover, inhibition of the nuclear transport by wheat germ agglutinin (an import inhibitor) and leptomycin B (an export inhibitor) induced premature senescence. These results suggest that Sp1 is an anti-senescence transcription factor in the telomere uncapping-induced senescence and that down-regulation of Sp1 leads to the senescence via down-regulation of the nuclear transport.
MeSH Terms
- Cellular Senescence
- Diploidy
- Fibroblasts
- Humans
- Sp1 Transcription Factor
- Telomeric Repeat Binding Protein 2
Keywords
- Nuclear transport
- Senescence
- Sp1
- TRF2ΔBΔM
- Telomere uncapping
Cell senescence is an important tumour suppressor mechanism and driver of ageing. Both functions are dependent on the development of the senescent phenotype, which involves an overproduction of pro-inflammatory and pro-oxidant signals. However, the exact mechanisms regulating these phenotypes remain poorly understood. Here, we show the critical role of mitochondria in cellular senescence. In multiple models of senescence, absence of mitochondria reduced a spectrum of senescence effectors and phenotypes while preserving ATP production via enhanced glycolysis. Global transcriptomic analysis by RNA sequencing revealed that a vast number of senescent-associated changes are dependent on mitochondria, particularly the pro-inflammatory phenotype. Mechanistically, we show that the ATM, Akt and mTORC1 phosphorylation cascade integrates signals from the DNA damage response (DDR) towards PGC-1β-dependent mitochondrial biogenesis, contributing to aROS-mediated activation of the DDR and cell cycle arrest. Finally, we demonstrate that the reduction in mitochondrial content in vivo, by either mTORC1 inhibition or PGC-1β deletion, prevents senescence in the ageing mouse liver. Our results suggest that mitochondria are a candidate target for interventions to reduce the deleterious impact of senescence in ageing tissues.
MeSH Terms
- Aging
- Animals
- Cell Line
- Humans
- Mice
- Mitochondria
- Models, Biological
- Phenotype
Keywords
- ageing
- inflammation
- mTOR
- mitochondria
- senescence
Human respiratory syncytial virus (HRSV) accounts for the majority of lower respiratory tract infections during infancy and childhood and is associated with significant morbidity and mortality. HRSV provokes a proliferation arrest and characteristic syncytia in cellular systems such as immortalized epithelial cells. We show here that HRSV induces the expression of DNA damage markers and proliferation arrest such as P-TP53, P-ATM, CDKN1A and γH2AFX in cultured cells secondary to the production of mitochondrial reactive oxygen species (ROS). The DNA damage foci contained γH2AFX and [[TP53BP1]], indicative of double-strand breaks (DSBs) and could be reversed by antioxidant treatments such as N-Acetylcysteine (NAC) or reduced glutathione ethyl ester (GSHee). The damage observed is associated with the accumulation of senescent cells, displaying a canonical senescent phenotype in both mononuclear cells and syncytia. In addition, we show signs of DNA damage and aging such as γH2AFX and [[CDKN2A]] expression in the respiratory epithelia of infected mice long after viral clearance. Altogether, these results show that HRSV triggers a DNA damage-mediated cellular senescence program probably mediated by oxidative stress. The results also suggest that this program might contribute to the physiopathology of the infection, tissue remodeling and aging, and might be associated to long-term consequences of HRSV infections.
MeSH Terms
- A549 Cells
- Acetylcysteine
- Animals
- Cell Line
- Cellular Senescence
- Cyclin-Dependent Kinase Inhibitor p16
- Cyclin-Dependent Kinase Inhibitor p18
- DNA Breaks, Double-Stranded
- DNA Damage
- Glutathione
- Histones
- Host-Pathogen Interactions
- Humans
- Mice
- Oxidative Stress
- Reactive Oxygen Species
- Respiratory Mucosa
- Respiratory Syncytial Virus Infections
- Respiratory Syncytial Virus, Human
Keywords
- DNA damage
- ROS
- cellular senescence
- human respiratory
- syncytial virus
Senescence stimuli activate multiple tumor suppressor pathways to initiate cycle arrest and a differentiation program characteristic of senescent cells. We performed a two-stage, gain-of-function screen to select for the genes whose enhanced expression can bypass replicative senescence. We uncovered multiple genes known to be involved in p53 and Rb regulation and ATM regulation, two components of the CST (CTC1-STN1-TEN1) complex involved in preventing telomere erosion, and genes such as REST and FOXO4 that have been implicated in aging. Among the new genes now implicated in senescence, we identified DLX2, a homeobox transcription factor that has been shown to be required for tumor growth and metastasis and is associated with poor cancer prognosis. Growth analysis showed that DLX2 expression led to increased cellular replicative life span. Our data suggest that DLX2 expression reduces the protein components of the TTI1/TTI2/TEL2 complex, a key complex required for the proper folding and stabilization of ATM and other members of the PIKK (phosphatidylinositol 3-kinase-related kinase) family kinase, leading to reduced ATM-p53 signaling and senescence bypass. We also found that the overexpression of DLX2 exhibited a mutually exclusive relationship with p53 alterations in cancer patients. Our functional screen identified novel players that may promote tumorigenesis by regulating the ATM-p53 pathway and senescence.
MeSH Terms
- Ataxia Telangiectasia Mutated Proteins
- Cell Line
- Cellular Senescence
- Computational Biology
- Gene Expression Regulation
- Homeodomain Proteins
- Humans
- Reproducibility of Results
- Signal Transduction
- Telomere Homeostasis
- Transcription Factors
- Transcriptional Activation
- Tumor Suppressor Protein p53
Keywords
- ATM
- genetic screen
- senescence
Previously we demonstrated that endometrium-derived human mesenchymal stem cells (hMESCs) via activation of the ATM/p53/p21/Rb pathway enter the premature senescence in response to oxidative stress. Down regulation effects of the key components of this signaling pathway, particularly ATM and p53, on a fate of stressed hMESCs have not yet been investigated. In the present study by using the specific inhibitors Ku55933 and Pifithrin-α, we confirmed implication of both ATM and p53 in H(2)O(2)-induced senescence of hMESCs. ATM or p53 down regulation was shown to modulate differently the cellular fate of H(2)O(2)-treated hMESCs. ATM inhibition allowed H(2)O(2)-stimulated hMESCs to escape the permanent cell cycle arrest due to loss of the functional ATM/p53/p21/Rb pathway, and induced bypass of mitosis and re-entry into S phase, resulting in tetraploid cells. On the contrary, suppression of the p53 transcriptional activity caused a pronounced cell death of H(2)O(2)-treated hMESCs via autophagy induction. The obtained data clearly demonstrate that down regulation of ATM or p53 shifts senescence of human endometrial stem cells toward tetraploidization or autophagy.
MeSH Terms
- Ataxia Telangiectasia Mutated Proteins
- Autophagy
- Cell Survival
- Cellular Senescence
- Endometrium
- Female
- Humans
- Hydrogen Peroxide
- Mesenchymal Stem Cells
- Morpholines
- Pyrones
- Tetraploidy
- Tumor Suppressor Protein p53
Keywords
- ATM kinase
- autophagy
- cellular senescence
- oxidative stress
- p53
- stem cells
- tetraploidization
Ataxia-telangiectasia (AT) is an autosomal recessive neurodegenerative disorder with immunodeficiency and an increased risk of developing cancer, caused by mutations in the ataxia-telangiectasia mutated (ATM) gene. Logically, blood relatives may also carry a pathogenic ATM mutation. Female carriers of such a mutation have an increased risk of breast cancer. Other health risks for carriers are suspected but have never been studied systematically. Consequently, evidence-based guidelines for carriers are not available yet. We systematically analyzed all literature and found that ATM mutation carriers have a reduced life expectancy because of mortality from cancer and ischemic heart diseases (RR 1.7, 95% CI 1.2-2.4) and an increased risk of developing cancer (RR 1.5, 95% CI 0.9-2.4), in particular breast cancer (RRwomen 3.0, 95% CI 2.1-4.5), and cancers of the digestive tract. Associations between ATM heterozygosity and other health risks have been suggested, but clear evidence is lacking. Based on these results, we propose that all female carriers of 40-50 years of age and female ATM c.7271T>G mutation carriers from 25 years of age onwards be offered intensified surveillance programs for breast cancer. Furthermore, all carriers should be made aware of lifestyle factors that contribute to the development of cardiovascular diseases and diabetes.
MeSH Terms
- Adult
- Ataxia Telangiectasia
- Ataxia Telangiectasia Mutated Proteins
- Breast Neoplasms
- Evidence-Based Medicine
- Female
- Gastrointestinal Neoplasms
- Gene Expression
- Genetic Counseling
- Genetic Predisposition to Disease
- Heterozygote
- Humans
- Life Expectancy
- Middle Aged
- Mutation
- Myocardial Ischemia
- Practice Guidelines as Topic
- Risk Factors
Keywords
- ATM protein
- ataxia-telangiectasia
- heterozygote
- risk factor
Cellular senescence is a terminal stress-activated program controlled by the p53 and p16(INK4a) tumor suppressor proteins. A striking feature of senescence is the senescence-associated secretory phenotype (SASP), a pro-inflammatory response linked to tumor promotion and aging. We have identified the transcription factor GATA4 as a senescence and SASP regulator. GATA4 is stabilized in cells undergoing senescence and is required for the SASP. Normally, GATA4 is degraded by p62-mediated selective autophagy, but this regulation is suppressed during senescence, thereby stabilizing GATA4. GATA4 in turn activates the transcription factor NF-κB to initiate the SASP and facilitate senescence. GATA4 activation depends on the DNA damage response regulators ATM and ATR, but not on p53 or p16(INK4a). GATA4 accumulates in multiple tissues, including the aging brain, and could contribute to aging and its associated inflammation.
MeSH Terms
- Adaptor Proteins, Signal Transducing
- Aging
- Animals
- Ataxia Telangiectasia Mutated Proteins
- Autophagy
- Brain
- Cell Cycle
- Cells, Cultured
- Cellular Senescence
- Cyclin-Dependent Kinase Inhibitor p16
- DNA Damage
- Fibroblasts
- GATA4 Transcription Factor
- Gene Expression Profiling
- Humans
- Inflammation
- Interleukin-1alpha
- Mice
- Mice, Inbred C57BL
- MicroRNAs
- NF-kappa B
- Phenotype
- Promoter Regions, Genetic
- Tumor Necrosis Factor Receptor-Associated Peptides and Proteins
- Tumor Suppressor Protein p53
Oocyte aging has a significant impact on reproductive outcomes both quantitatively and qualitatively. However, the molecular mechanisms underlying the age-related decline in reproductive success have not been fully addressed. BRCA is known to be involved in homologous DNA recombination and plays an essential role in double-strand DNA break repair. Given the growing body of laboratory and clinical evidence, we performed a systematic review on the current understanding of the role of DNA repair in human reproduction. We find that BRCA mutations negatively affect ovarian reserve based on convincing evidence from in vitro and in vivo results and prospective studies. Because decline in the function of the intact gene occurs at an earlier age, women with BRCA1 mutations exhibit accelerated ovarian aging, unlike those with BRCA2 mutations. However, because of the still robust function of the intact allele in younger women and because of the masking of most severe cases by prophylactic oophorectomy or cancer, it is less likely one would see an effect of BRCA mutations on fertility until later in reproductive age. The impact of BRCA2 mutations on reproductive function may be less visible because of the delayed decline in the function of normal BRCA2 allele. BRCA1 function and ataxia-telangiectasia-mutated (ATM)-mediated DNA repair may also be important in the pathogenesis of age-induced increase in aneuploidy. BRCA1 is required for meiotic spindle assembly, and cohesion function between sister chromatids is also regulated by ATM family member proteins. Taken together, these findings strongly suggest the implication of BRCA and DNA repair malfunction in ovarian aging.
MeSH Terms
- Animals
- BRCA1 Protein
- BRCA2 Protein
- DNA Repair
- Female
- Fertility
- Genes, BRCA2
- Humans
- Infertility
- Mice
- Ovary
Keywords
- BRCA
- BRCA1
- BRCA2
- fertility
- infertility
- mechanisms of ovarian aging
- mutations
- oocyte
- oocyte DNA repair
- ovarian reserve
Cardiovascular disease is a severe threat to human health and life. Among many risk factors of cardiovascular disease, genetic or gene-based ones are drawing more and more attention in recent years. Accumulated evidence has demonstrated that the loss or mutation of ataxia telangiectasia mutated (ATM) gene can result in DNA damage repair dysfunctions, telomere shortening, decreased antioxidant capacity, insulin resistance, increased lipid levels, etc., and thus can promote the occurrence of cardiovascular risk factors, such as aging, atherosclerosis and metabolic syndrome. In this review, we discusses the possible mechanisms between ATM gene and cardiovascular risk factors, which could be helpful to the related research and clinical application.
MeSH Terms
- Aging
- Ataxia Telangiectasia Mutated Proteins
- Cardiovascular Diseases
- DNA Damage
- DNA Repair
- Humans
- Mutation
- Risk Factors
The stem cell genomic stability forms the basis for robust tissue homeostasis, particularly in high-turnover tissues. For the genomic stability, DNA damage response (DDR) is essential. This study was focused on the role of two major DDR-related factors, ataxia telangiectasia-mutated (ATM) and ATM- and RAD3-related (ATR) kinases, in the maintenance of intestinal stem cells (ISCs) in the adultDrosophila midgut. We explored the role of ATM and ATR, utilizing immunostaining with an anti-pS/TQ antibody as an indicator of ATM/ATR activation, γ-irradiation as a DNA damage inducer, and the UAS/GAL4 system for cell type-specific knockdown of ATM, ATR, or both during adulthood. The results showed that the pS/TQ signals got stronger with age and after oxidative stress. The pS/TQ signals were found to be more dependent on ATR rather than on ATM in ISCs/enteroblasts (EBs). Furthermore, an ISC/EB-specific knockdown of ATR, ATM, or both decreased the number of ISCs and oxidative stress-induced ISC proliferation. The phenotypic changes that were caused by the ATR knockdown were more pronounced than those caused by the ATM knockdown; however, our data indicate that ATR and ATM are both needed for ISC maintenance and proliferation; ATR seems to play a bigger role than does ATM.
MeSH Terms
- Adult Stem Cells
- Aging
- Animals
- Ataxia Telangiectasia Mutated Proteins
- Cell Cycle Proteins
- Drosophila
- Drosophila Proteins
- Immunohistochemistry
- Intestines
- Protein-Serine-Threonine Kinases
- Stem Cells
Keywords
- ATM/ATR
- DNA damage response
- Drosophila
- aging
- intestinal stem cell
Cells exposed to genotoxic stress induce cellular senescence through a DNA damage response (DDR) pathway regulated by ATM kinase and reactive oxygen species (ROS). Here, we show that the regulatory roles for ATM kinase and ROS differ during induction and maintenance of cellular senescence. Cells treated with different genotoxic agents were analyzed using specific pathway markers and inhibitors to determine that ATM kinase activation is directly proportional to the dose of the genotoxic stress and that senescence initiation is not dependent on ROS or the p53 status of cells. Cells in which ROS was quenched still activated ATM and initiated the DDR when insulted, and progressed normally to senescence. By contrast, maintenance of a viable senescent state required the presence of ROS as well as activated ATM. Inhibition or removal of either of the components caused cell death in senescent cells, through a deregulated ATM-ROS axis. Overall, our work demonstrates existence of an intricate temporal hierarchy between genotoxic stress, DDR and ROS in cellular senescence. Our model reports the existence of different stages of cellular senescence with distinct regulatory networks.
MeSH Terms
- Ataxia Telangiectasia Mutated Proteins
- Bromodeoxyuridine
- Cellular Senescence
- DNA Damage
- Gene Expression Regulation
- HeLa Cells
- Humans
- Phosphorylation
- Reactive Oxygen Species
- Signal Transduction
- Tumor Suppressor Protein p53
Keywords
- ATM kinase
- Cellular senescence
- DNA damage response
- Reactive oxygen species
Oxidative stress and persistent DNA damage response contribute to cellular senescence, a degeneration process critically involving ataxia telangiectasia-mutated (ATM) and p53. Selenoprotein H (SelH), a nuclear selenoprotein, is proposed to carry redox and transactivation domains. To determine the role of SelH in genome maintenance, shRNA knockdown was employed in human normal and immortalized cell lines. SelH shRNA MRC-5 diploid fibroblasts under ambient O2 displayed a distinct profile of senescence including β-galactosidase expression, autofluorescence, growth inhibition, and ATM pathway activation. Such senescence phenotypes were alleviated in the presence of ATM kinase inhibitors, by p53 shRNA knockdown, or by maintaining the cells under 3% O2. During the course of 5-day recovery, the induction of phospho-ATM on Ser-1981 and γH2AX by H2O2 treatment (20 μm) subsided in scrambled shRNA but exacerbated in SelH shRNA MRC-5 cells. Results from clonogenic assays demonstrated hypersensitivity of SelH shRNA HeLa cells to paraquat and H2O2, but not to hydroxyurea, neocarzinostatin, or camptothecin. While SelH mRNA expression was induced by H2O2 treatment, SelH-GFP did not mobilize to sites of oxidative DNA damage. The glutathione level was lower in SelH shRNA than scrambled shRNA HeLa cells, and the H2O2-induced cell death was rescued in the presence of N-acetylcysteine, a glutathione precursor. Altogether, SelH protects against cellular senescence to oxidative stress through a genome maintenance pathway involving ATM and p53.
MeSH Terms
- Acetylcysteine
- Ataxia Telangiectasia Mutated Proteins
- Cell Line
- Cellular Senescence
- DNA-Binding Proteins
- Fibroblasts
- Gene Expression Regulation
- Genome, Human
- Genomic Instability
- HeLa Cells
- Humans
- Hydrogen Peroxide
- Oxidation-Reduction
- Oxidative Stress
- Paraquat
- Protein Kinase Inhibitors
- RNA, Small Interfering
- Recombinant Fusion Proteins
- Selenoproteins
- Signal Transduction
- Tumor Suppressor Protein p53
- beta-Galactosidase
Keywords
- Ataxia Telangiectasia
- Reactive Oxygen Species (ROS)
- Selenium
- Senescence
- p53
Telomeres are specialized structures protecting chromosomes against genome instability. Telomeres shorten with cell division, and replicative senescence is induced when telomeres are badly eroded. Whereas TRF2 (telomeric-repeat binding factor 2), ATM (ataxia telangiectasia mutated) and p53 have been identified involved in senescence induction, how it is triggered remains unclear. Here, we propose an integrated model associating telomere loss with senescence trigger. We characterize the dynamics of telomere shorting and the p53-centered regulatory network. We show that senescence is initiated in a switch-like manner when both the shortest telomere becomes uncapped and the TRF2-ATM-p53-Siah1 positive feedback loop is switched on. This work provides a coherent picture of senescence induction in terms of telomere shortening and p53 activation.
MeSH Terms
- Ataxia Telangiectasia Mutated Proteins
- Diploidy
- Down-Regulation
- Feedback, Physiological
- Fibroblasts
- Humans
- Models, Biological
- Nuclear Proteins
- Phosphorylation
- Proto-Oncogene Proteins c-mdm2
- Telomere Shortening
- Telomeric Repeat Binding Protein 2
- Tumor Suppressor Protein p53
- Ubiquitin-Protein Ligases
Keywords
- Bistable switch
- Regulatory network
- Replicative senescence
- Telomere shortening
- p53 activation
Recently, several studies indicated that senescent tumor cells are resistant to apoptosis in chemotherapy. They may return to cell cycle, thus act as stumbling blocks in anticancer treatments. In the present study, we found that, in human colorectal cancer cells, low-dose camptothecin (CPT) simultaneously induced autophagy and premature senescence through AMPK-TSC2-mTOR pathway and ATM-Chk2-p53-p21 pathway respectively. What's important is the suppression of autophagy substantially increased apoptosis and greatly attenuated senescence possibly by blocking p53/p21 pathway, which suggests that autophagy plays an indispensable role in sustaining cell senescence caused by low-dose CPT. The combination of low-dose CPT and autophagy inhibitor, a way to lead senescent cells to die, would be potentially valuable in cancer therapy.
MeSH Terms
- AMP-Activated Protein Kinases
- Adenine
- Antineoplastic Agents
- Apoptosis
- Ataxia Telangiectasia Mutated Proteins
- Autophagy
- Camptothecin
- Cell Line, Tumor
- Cellular Senescence
- Chloroquine
- Class III Phosphatidylinositol 3-Kinases
- Colorectal Neoplasms
- Drug Resistance, Neoplasm
- Enzyme Inhibitors
- Humans
- Lysosomes
- Neoplasm Proteins
- Osmolar Concentration
- Signal Transduction
- Tumor Suppressor Protein p53
Keywords
- Apoptosis
- Autophagy
- DNA damage response
- Human colorectal cancer cells
- Low-dose chemotherapy
- Senescence
Oxidative stress-induced retinal pigment epithelium (RPE) senescence is one of the important factors in the pathogenesis of age-related macular degeneration (AMD). This study aimed to develop a new antisenescence-based intervention and clarify its possible molecular mechanism. A cell premature senescence model was established in both primary RPE cells and ARPE-19 cells by exposure of the cells to pulsed H₂O₂ stress for 5 days, and confirmed with senescence-associated β-galactosidase (SA-β-gal) staining. The final concentration of fullerenol (Fol) in the cell culture system was 5 μg/mL. Cellular redox status was determined by the examination of cellular reactive oxygen species (ROS) staining, catalase activity, and the ratio of reduced to oxidized glutathione, respectively. Deoxyribonucleic acid double-strand breaks were determined by quantitative analysis of γH₂AX. Cell cycle analysis was performed with flow cytometry. SIRT1 activity was examined with SIRT1 Assay Kit. SIRT1 overexpression and knockdown in ARPE-19 cells were performed with lentiviral-mediated infection. Pulsed H₂O₂ exposure triggered the acetylation of p53 at lysine 382 (K382) and subsequent increase in its target p21(Waf1/Cip1). It also increased the number of accumulated phospho-γH2AX foci and the level of phosphor-ATM in RPE cells. Fullerenol protected the RPE cells, as it reduced the number of positive SA-β-gal-staining cells, alleviated the depletion of cellular antioxidants, and reduced genomic DNA damage. Its mechanism might involve the activation of deacetylase SIRT1, resulting in decreased levels of acetyl-p53 and p21(Waf1/Cip1). The roles of SIRT1 in protecting cells in response to Fol were further confirmed by applications of SIRT1 activator (resveratrol) and inhibitors (nicotinamide and sirtinol), and through SIRT1 overexpression and knockdown. Fullerenol could rescue RPE cells from oxidative stress-induced senescence through its antioxidation activity and the activation of SIRT1. The protective effect of Fol is useful for the development of new strategies to treat oxidative stress-related retinal diseases like AMD.
MeSH Terms
- Animals
- Antioxidants
- Catalase
- Cell Cycle
- Cell Line
- Cell Survival
- Cellular Senescence
- DNA Breaks, Double-Stranded
- Flow Cytometry
- Fullerenes
- Gene Silencing
- Genetic Vectors
- Glutathione
- Glutathione Disulfide
- Histones
- Humans
- Hydrogen Peroxide
- Oxidants
- Oxidative Stress
- Reactive Oxygen Species
- Real-Time Polymerase Chain Reaction
- Retinal Pigment Epithelium
- Sirtuin 1
- Swine
Keywords
- DNA damage
- RPE senescence
- SIRT1
- fullerenol
- oxidative stress
TRF2 is a component of shelterin, the protein complex that protects the ends of mammalian chromosomes. TRF2 is essential for telomere capping owing to its roles in suppressing an ATM-dependent DNA damage response (DDR) at chromosome ends and inhibiting end-to-end chromosome fusions. Mice deficient for TRF2 are early embryonic lethal. However, the role of TRF2 in later stages of development and in the adult organism remains largely unaddressed, with the exception of liver, where TRF2 was found to be dispensable for maintaining tissue function. Here, we study the impact of TRF2 conditional deletion in stratified epithelia by generating the TRF2(∆/∆) -K5-Cre mouse model, which targets TRF2 deletion to the skin from embryonic day E11.5. In marked contrast to TRF2 deletion in the liver, TRF2(∆/∆) -K5-Cre mice show lethality in utero reaching 100% lethality perinataly. At the molecular and cellular level, TRF2 deletion provokes induction of an acute DDR at telomeres, leading to activation of p53 signaling pathways and to programed cell death since the time of Cre expression at E11.5. Unexpectedly, neither inhibition of the NHEJ pathway by abrogation of 53BP1 nor inhibition of DDR by p53 deficiency rescued these severe phenotypes. Instead, TRF2 deletion provokes an extensive epidermal cell death accompanied by severe inflammation already at E16.5 embryos, which are independent of p53. These results are in contrast with conditional deletion of TRF1 and TPP1 in the skin, where p53 deficiency rescued the associated skin phenotypes, highlighting the comparatively more essential role of TRF2 in skin homeostasis.
MeSH Terms
- Aging
- Animals
- Apoptosis
- Chromosomal Proteins, Non-Histone
- Cyclin-Dependent Kinase Inhibitor p21
- DNA Damage
- DNA-Binding Proteins
- Embryo Loss
- Embryonic Development
- Epidermis
- Epithelium
- Gene Deletion
- Homeostasis
- Integrases
- Keratin-5
- Keratinocytes
- Mice
- Skin
- Stem Cells
- Telomere
- Telomere Homeostasis
- Telomeric Repeat Binding Protein 2
- Tumor Suppressor Protein p53
- Tumor Suppressor p53-Binding Protein 1
Keywords
- 53BP1
- DNA damage
- TRF2
- Telomeres
- p53
- skin embryonic development
Wip1 (protein phosphatase Mg(2 )/Mn(2 )-dependent 1D, Ppm1d) is a nuclear serine/threonine protein phosphatase that is induced by p53 following the activation of DNA damage response (DDR) signaling. Ppm1d(-/-) mouse embryonic fibroblasts (MEFs) exhibit premature senescence under conventional culture conditions; however, little is known regarding the role of Wip1 in regulating cellular senescence. In this study, we found that even at a representative physiological concentration of 3% O2, Ppm1d(-/-) MEFs underwent premature cellular senescence that depended on the functional activation of p53. Interestingly, Ppm1d(-/-) MEFs showed increased H2AX phosphorylation levels without increased levels of reactive oxygen species (ROS) or DNA base damage compared with wild-type (Wt) MEFs, suggesting a decreased threshold for DDR activation or sustained DDR activation during recovery. Notably, the increased H2AX phosphorylation levels observed in Ppm1d(-/-) MEFs were primarily associated with S-phase cells and predominantly dependent on the activation of ATM. Moreover, these same phenotypes were observed when Wt and Ppm1d(-/-) MEFs were either transiently or chronically exposed to low levels of agents that induce replication-mediated double-stranded breaks. These findings suggest that Wip1 prevents the induction of cellular senescence at physiological oxygen levels by attenuating DDR signaling in response to endogenous double-stranded breaks that form during DNA replication.
MeSH Terms
- Aging, Premature
- Animals
- Cells, Cultured
- DNA Damage
- DNA Replication
- Histones
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Oxygen
- Phosphoprotein Phosphatases
- Phosphorylation
- Protein Phosphatase 2C
- Reactive Oxygen Species
- S Phase
- Signal Transduction
- Tumor Suppressor Protein p53
Keywords
- ATM
- DNA damage response
- Wip1
- camptothecin
- cellular senescence
- p53
CARF is an ARF-binding protein that has been shown to regulate the p53-p21-HDM2 pathway. CARF overexpression was shown to cause growth arrest of human cancer cells and premature senescence of normal cells through activation of the p53 pathway. Because replicative senescence involves permanent withdrawal from the cell cycle in response to DNA damage response-mediated signaling, in the present study we investigated the relationship between CARF and the cell cycle and whether it is involved in the DNA damage response. We demonstrate that the half-life of CARF protein is less than 60 min, and that in cycling cells CARF levels are highest in G2 and early prophase. Serially passaged normal human skin and stromal fibroblasts showed upregulation of CARF during replicative senescence. Induction of G1 growth arrest and senescence by a variety of drugs was associated with increase in CARF expression at the transcriptional and translational level and was seen to correlate with increase in DNA damage response and checkpoint proteins, ATM, ATR, CHK1, CHK2, γH2AX, p53 and p21. Induction of growth arrest by oncogenic RAS and shRNA-mediated knockdown of TRF2 in cancer cells also caused upregulation of CARF. We conclude that CARF is associated with DNA damage response and checkpoint signaling pathways.
MeSH Terms
- Antineoplastic Agents
- Apoptosis
- Apoptosis Regulatory Proteins
- Blotting, Western
- Cell Cycle Checkpoints
- Cell Cycle Proteins
- Cell Proliferation
- Cells, Cultured
- Cellular Senescence
- DNA Damage
- Fibroblasts
- Fluorescent Antibody Technique
- Humans
- Neoplasms
- Promoter Regions, Genetic
- RNA, Messenger
- RNA, Small Interfering
- RNA-Binding Proteins
- Real-Time Polymerase Chain Reaction
- Reverse Transcriptase Polymerase Chain Reaction
- Skin
- Stromal Cells
- Telomeric Repeat Binding Protein 2
Keywords
- CARF
- DNA damage response
- Mechanism
- Senescence
- Upregulation
There is increasing evidence that the thyroid hormone (TH) receptors (THRs) can play a role in aging, cancer and degenerative diseases. In this paper, we demonstrate that binding of TH T3 (triiodothyronine) to [[THRB]] induces senescence and deoxyribonucleic acid (DNA) damage in cultured cells and in tissues of young hyperthyroid mice. T3 induces a rapid activation of ATM (ataxia telangiectasia mutated)/PRKAA (adenosine monophosphate-activated protein kinase) signal transduction and recruitment of the NRF1 (nuclear respiratory factor 1) and [[THRB]] to the promoters of genes with a key role on mitochondrial respiration. Increased respiration leads to production of mitochondrial reactive oxygen species, which in turn causes oxidative stress and DNA double-strand breaks and triggers a DNA damage response that ultimately leads to premature senescence of susceptible cells. Our findings provide a mechanism for integrating metabolic effects of THs with the tumor suppressor activity of [[THRB]], the effect of thyroidal status on longevity, and the occurrence of tissue damage in hyperthyroidism.
MeSH Terms
- AMP-Activated Protein Kinases
- Aging
- Animals
- Ataxia Telangiectasia Mutated Proteins
- Cells, Cultured
- DNA Breaks, Double-Stranded
- DNA Damage
- DNA Repair
- Fibroblasts
- Mice
- Mitochondria
- Nuclear Respiratory Factor 1
- Oxidative Stress
- Promoter Regions, Genetic
- Signal Transduction
- Thyroid Hormone Receptors beta
- Triiodothyronine
- Tumor Suppressor Protein p53
Oligonucleotides homologous to 3'-telomere overhang (T-oligos) trigger inherent telomere-based DNA damage responses mediated by p53 and/or ATM and induce senescence or apoptosis in various cancerous cells. However, T-oligo has limited stability in vivo due to serum and intracellular nucleases. To develop T-oligo as an innovative, effective therapeutic drug and to understand its mechanism of action, we investigated the antitumor effects of T-oligo or T-oligo complexed with a novel cationic alpha helical peptide, PVBLG-8 (PVBLG), in a p53 null melanoma cell line both in vitro and in vivo. The uptake of T-oligo by MM-AN cells was confirmed by immunofluorescence, and fluorescence-activated cell sorting analysis indicated that the T-oligo-PVBLG nanocomplex increased uptake by 15-fold. In vitro results showed a 3-fold increase in MM-AN cell growth inhibition by the T-oligo-PVBLG nanocomplex compared with T-oligo alone. Treatment of preformed tumors in immunodeficient mice with the T-oligo-PVBLG nanocomplex resulted in a 3-fold reduction in tumor volume compared with T-oligo alone. This reduction in tumor volume was associated with decreased vascular endothelial growth factor expression and induction of thrombospondin-1 expression and apoptosis. Moreover, T-oligo treatment downregulated procaspase-3 and procaspase-7 and increased catalytic activity of caspase-3 by 4-fold in MM-AN cells. Furthermore, T-oligo induced a 10-fold increase of senescence and upregulated the melanoma tumor-associated antigens MART-1, tyrosinase, and thrombospondin-1 in MM-AN cells, which are currently being targeted for melanoma immunotherapy. Interestingly, siRNA-mediated knockdown of p73 (4-10-fold) abolished this upregulation of tumor-associated antigens. In summary, we suggest a key role of p73 in mediating the anticancer effects of T-oligo and introduce a novel nanoparticle, the T-oligo-PVBLG nanocomplex, as an effective anticancer therapeutic.
MeSH Terms
- Animals
- Cell Line, Tumor
- Drug Combinations
- Male
- Melanoma
- Mice
- Mice, Nude
- Nanocapsules
- Oligonucleotides
- Particle Size
- Peptides
- Treatment Outcome
Keywords
- T-oligo
- angiogenesis
- apoptosis
- melanoma
- senescence
Cardiovascular disease (CVD) is a major cause of death in smokers, particularly in those with chronic obstructive pulmonary disease (COPD). Circulating endothelial progenitor cells (EPC) are required for endothelial homeostasis, and their dysfunction contributes to CVD. To investigate EPC dysfunction in smokers, we isolated and expanded blood outgrowth endothelial cells (BOEC) from peripheral blood samples from healthy nonsmokers, healthy smokers, and COPD patients. BOEC from smokers and COPD patients showed increased DNA double-strand breaks and senescence compared to nonsmokers. Senescence negatively correlated with the expression and activity of sirtuin-1 (SIRT1), a protein deacetylase that protects against DNA damage and cellular senescence. Inhibition of DNA damage response by silencing of ataxia telangiectasia mutated (ATM) kinase resulted in upregulation of SIRT1 expression and decreased senescence. Treatment of BOEC from COPD patients with the SIRT1 activator resveratrol or an ATM inhibitor (KU-55933) also rescued the senescent phenotype. Using an in vivo mouse model of angiogenesis, we demonstrated that senescent BOEC from COPD patients are dysfunctional, displaying impaired angiogenic ability and increased apoptosis compared to cells from healthy nonsmokers. Therefore, this study identifies epigenetic regulation of DNA damage and senescence as pathogenetic mechanisms linked to endothelial progenitors' dysfunction in smokers and COPD patients. These defects may contribute to vascular disease and cardiovascular events in smokers and could therefore constitute therapeutic targets for intervention.
MeSH Terms
- Adult
- Aged
- Aged, 80 and over
- Cardiovascular Diseases
- Case-Control Studies
- Cellular Senescence
- DNA Damage
- Endothelial Cells
- Female
- Humans
- Male
- Middle Aged
- Oxidative Stress
- Pulmonary Disease, Chronic Obstructive
- RNA Interference
- Smoking
- Stem Cells
Keywords
- Ataxia telangiectasia-mutated kinase
- Cellular senescence
- DNA damage response
- Endothelial progenitor cells
- Sirtuin
- Smoking
Maternal embryonic leucine zipper kinase (MELK) belongs to the subfamily of AMP-activated Ser/Thr protein kinases. The expression of MELK is very high in glioblastoma-type brain tumors, but it is not clear how this contributes to tumor growth. Here we show that the siRNA-mediated loss of MELK in U87 MG glioblastoma cells causes a G1/S phase cell cycle arrest accompanied by cell death or a senescence-like phenotype that can be rescued by the expression of siRNA-resistant MELK. This cell cycle arrest is mediated by an increased expression of p21(WAF1/CIP1), an inhibitor of cyclin-dependent kinases, and is associated with the hypophosphorylation of the retinoblastoma protein and the down-regulation of E2F target genes. The increased expression of p21 can be explained by the consecutive activation of ATM (ataxia telangiectasia mutated), Chk2, and p53. Intriguingly, the activation of p53 in MELK-deficient cells is not due to an increased stability of p53 but stems from the loss of MDMX (mouse double minute-X), an inhibitor of p53 transactivation. The activation of the ATM-Chk2 pathway in MELK-deficient cells is associated with the accumulation of DNA double-strand breaks during replication, as demonstrated by the appearance of γH2AX foci. Replication stress in these cells is also illustrated by an increased number of stalled replication forks and a reduced fork progression speed. Our data indicate that glioblastoma cells have elevated MELK protein levels to better cope with replication stress during unperturbed S phase. Hence, MELK inhibitors hold great potential for the treatment of glioblastomas as such or in combination with DNA-damaging therapies.
MeSH Terms
- Animals
- Brain Neoplasms
- Cell Line, Tumor
- Cellular Senescence
- Cyclin-Dependent Kinase Inhibitor p21
- DNA Breaks, Double-Stranded
- DNA Replication
- Gene Knockdown Techniques
- Glioblastoma
- Histones
- Mice
- Models, Biological
- Phenotype
- Protein-Serine-Threonine Kinases
- Retinoblastoma Protein
- S Phase
- Signal Transduction
- Stress, Physiological
- Tumor Suppressor Protein p53
- Up-Regulation
Keywords
- Cell Cycle
- DNA Damage
- Glioblastoma
- MELK
- Protein Kinases
- Replication Stress
- Senescence
- p21/WAF1/CIP1
Reactive oxygen species (ROS) play complex roles in aging, having both damaging effects and signaling functions. Transiently elevating mitochondrial stress, including mitochondrial ROS (mtROS), elicits beneficial responses that extend lifespan. However, these adaptive, longevity-signaling pathways remain poorly understood. We show here that Tel1p and Rad53p, homologs of the mammalian DNA damage response kinases ATM and Chk2, mediate a hormetic mtROS longevity signal that extends yeast chronological lifespan. This pathway senses mtROS in a manner distinct from the nuclear DNA damage response and ultimately imparts longevity by inactivating the histone demethylase Rph1p specifically at subtelomeric heterochromatin, enhancing binding of the silencing protein Sir3p, and repressing subtelomeric transcription. These results demonstrate the existence of conserved mitochondria-to-nucleus stress-signaling pathways that regulate aging through epigenetic modulation of nuclear gene expression.
MeSH Terms
- Cell Cycle Proteins
- Checkpoint Kinase 2
- DNA Damage
- DNA Repair
- Epigenomics
- Gene Silencing
- Histone Demethylases
- Intracellular Signaling Peptides and Proteins
- Longevity
- Mitochondria
- Protein Binding
- Protein-Serine-Threonine Kinases
- Reactive Oxygen Species
- Repressor Proteins
- Saccharomyces cerevisiae
- Saccharomyces cerevisiae Proteins
- Signal Transduction
- Silent Information Regulator Proteins, Saccharomyces cerevisiae
Human ageing is associated with decreased cellular plasticity and adaptability. Changes in alternative splicing with advancing age have been reported in man, which may arise from age-related alterations in splicing factor expression. We determined whether the mRNA expression of key splicing factors differed with age, by microarray analysis in blood from two human populations and by qRT-PCR in senescent primary fibroblasts and endothelial cells. Potential regulators of splicing factor expression were investigated by siRNA analysis. Approximately one third of splicing factors demonstrated age-related transcript expression changes in two human populations. Ataxia Telangiectasia Mutated (ATM) transcript expression correlated with splicing factor expression in human microarray data. Senescent primary fibroblasts and endothelial cells also demonstrated alterations in splicing factor expression, and changes in alternative splicing. Targeted knockdown of the ATM gene in primary fibroblasts resulted in up-regulation of some age-responsive splicing factor transcripts. We conclude that isoform ratios and splicing factor expression alters with age in vivo and in vitro, and that ATM may have an inhibitory role on the expression of some splicing factors. These findings suggest for the first time that ATM, a core element in the DNA damage response, is a key regulator of the splicing machinery in man.
MeSH Terms
- Adolescent
- Adult
- Aged
- Aged, 80 and over
- Aging
- Alternative Splicing
- Ataxia Telangiectasia Mutated Proteins
- Cellular Senescence
- DNA Damage
- Fibroblasts
- Gene Expression Regulation
- Heterogeneous Nuclear Ribonucleoprotein A1
- Heterogeneous-Nuclear Ribonucleoprotein Group A-B
- Humans
- Italy
- Mexico
- Middle Aged
- Nerve Tissue Proteins
- Nuclear Proteins
- Oligonucleotide Array Sequence Analysis
- Protein Isoforms
- RNA, Messenger
- RNA, Small Interfering
- RNA-Binding Proteins
- Reverse Transcriptase Polymerase Chain Reaction
- Serine-Arginine Splicing Factors
- Young Adult
Keywords
- ATM
- Ageing
- Ataxia Telangiectasia Mutated gene
- Heterogeneous nuclear ribonucleoproteins
- Human
- LMNA
- Lamin A/C gene
- RT-PCR
- Reverse Transcription PCR
- SR splicing factor
- SRSF
- Splicing
- TLDA
- TaqMan Low Density Array
- hnRNP
- qRT-PCR
- quantitative real-time PCR
- siRNA
- small interfering RNA
ATM (ataxia-telangiectasia mutated) is a large protein kinase whose best-known function is as a participant in the process of DNA damage repair, specifically lesions that result in double strand breaks. In the cells of the nervous system, however, the symptoms of children with ataxia-telangiectasia and the phenotypes of mice with engineered mutations in their ATM gene argue for a broader range of protein functions. ATM is now appreciated to play a role in vesicle dynamics as well as in the maintenance of the epigenetic code of histone modifications. Finally, the decline of ATM levels with age suggest that late onset neurodegenerative diseases may owe part of their pathogenesis to deficits in ATM signaling. Evidence from the location of HDAC4 in the hippocampal pyramidal cells of the Alzheimer's disease brain supports this hypothesis. These multiple functions of the ATM protein are in keeping with the complex multi-system nature of the symptoms of ataxia-telangiectasia and encourage us to look beyond DNA damage for the full understanding of the disease and its consequences.
MeSH Terms
- Aging
- Animals
- Ataxia Telangiectasia
- Ataxia Telangiectasia Mutated Proteins
- Child
- DNA Damage
- DNA Repair
- Disease Models, Animal
- Epigenesis, Genetic
- Histone Deacetylases
- Humans
- Mutation
- Nervous System
- Neurons
- Repressor Proteins
- Signal Transduction
Keywords
- Alzheimer's disease
- Ataxia-telangiectasia
- DNA damage
- Epigenetics
- Glutamine
Human ATRX mutations are associated with cognitive deficits, developmental abnormalities, and cancer. We show that the Atrx-null embryonic mouse brain accumulates replicative damage at telomeres and pericentromeric heterochromatin, which is exacerbated by loss of p53 and linked to ATM activation. ATRX-deficient neuroprogenitors exhibited higher incidence of telomere fusions and increased sensitivity to replication stress-inducing drugs. Treatment of Atrx-null neuroprogenitors with the G-quadruplex (G4) ligand telomestatin increased DNA damage, indicating that ATRX likely aids in the replication of telomeric G4-DNA structures. Unexpectedly, mutant mice displayed reduced growth, shortened life span, lordokyphosis, cataracts, heart enlargement, and hypoglycemia, as well as reduction of mineral bone density, trabecular bone content, and subcutaneous fat. We show that a subset of these defects can be attributed to loss of ATRX in the embryonic anterior pituitary that resulted in low circulating levels of thyroxine and IGF-1. Our findings suggest that loss of ATRX increases DNA damage locally in the forebrain and anterior pituitary and causes tissue attrition and other systemic defects similar to those seen in aging.
MeSH Terms
- Aging
- Animals
- Bone and Bones
- Brain
- Cognition Disorders
- DNA Damage
- DNA Helicases
- Female
- Fibroblasts
- G-Quadruplexes
- Genotype
- Heterochromatin
- Insulin-Like Growth Factor I
- Ligands
- Longevity
- Male
- Mice
- Mice, Transgenic
- Microscopy, Fluorescence
- Nuclear Proteins
- Oxazoles
- Phenotype
- Stem Cells
- Telomere
- Thyroxine
- X-linked Nuclear Protein
Chronic inflammation is implicated in the pathogenesis of AMD. The source of chronic inflammation is often attributed to the progressive activation of immune cells over time. However, recent studies have shown that senescent cells can alter tissue microenvironment via secretion of growth factors, proteases, and inflammatory cytokines and might be an additional source of chronic inflammation. We hypothesized that altered secretory pattern in Aβ-induced senescent RPE cells may contribute to compromised RPE barrier integrity and chronic inflammation in AMD. Senescence was assessed by measuring the SA-β-Galactosidase activity, the expressions of p16(INK4a) and ATM, and cell cycle analysis. Expressions of IL-8 and MMPs were analyzed by RT-PCR, ELISA, and gelatin zymography. The barrier structures of RPE cells were detected by actin-tracker, ZO-1, claudin-19, occludin immunochemistry, and Western blot; barrier function was analyzed by measuring transepithelial resistance (TER) and transepithelial diffusion rate of FITC-dextran. For inhibitory studies, MMP-9 was inhibited by RNA interference strategy. Aβ promotes RPE cells to enter senescence and secrete higher concentrations of IL-8 and MMP-9. Secretion of MMP-9 is associated with compromised barrier integrity and with processing of IL-8 to a more activated form. Silence of MMP-9 preserved the barrier integrity of senescent RPE cells. The altered secretory phenotype of senescent RPE cells may contribute to age-related inflammation in AMD. Chinese Abstract.
MeSH Terms
- Amyloid beta-Peptides
- Cellular Microenvironment
- Cellular Senescence
- Chronic Disease
- Epithelial Cells
- Fetus
- Humans
- Interleukin-8
- Macular Degeneration
- Matrix Metalloproteinase 9
- Occludin
- Peptide Fragments
- RNA, Small Interfering
- Retinal Pigment Epithelium
- Retinitis
- Zonula Occludens-1 Protein
Keywords
- age-related macular degeneration (AMD)
- amyloid-beta (Aβ)
- inflammation
- senescence
The DNA damage response (DDR) rapidly recognizes DNA lesions and initiates the appropriate cellular programs to maintain genome integrity. This includes the coordination of cell cycle checkpoints, transcription, translation, DNA repair, metabolism, and cell fate decisions, such as apoptosis or senescence (Jackson and Bartek, 2009). DNA double-strand breaks (DSBs) represent one of the most cytotoxic DNA lesions and defects in their metabolism underlie many human hereditary diseases characterized by genomic instability (Stracker and Petrini, 2011; McKinnon, 2012). Patients with hereditary defects in the DDR display defects in development, particularly affecting the central nervous system, the immune system and the germline, as well as aberrant metabolic regulation and cancer predisposition. Central to the DDR to DSBs is the ataxia-telangiectasia mutated (ATM) kinase, a master controller of signal transduction. Understanding how ATM signaling regulates various aspects of the DDR and its roles in vivo is critical for our understanding of human disease, its diagnosis and its treatment. This review will describe the general roles of ATM signaling and highlight some recent advances that have shed light on the diverse roles of ATM and related proteins in human disease.
Keywords
- AT like disease
- ATM
- DNA repair
- Mre11 complex
- Nijmegen breakage syndrome
- apoptosis
- ataxia-telangiectasia
- senescence
Neurodegeneration is a hallmark of the human disease ataxia-telangiectasia (A-T) that is caused by mutation of the A-T mutated (ATM) gene. We have analyzed Drosophila melanogaster ATM mutants to determine the molecular mechanisms underlying neurodegeneration in A-T. Previously, we found that ATM mutants upregulate the expression of innate immune response (IIR) genes and undergo neurodegeneration in the central nervous system. Here, we present evidence that activation of the IIR is a cause of neurodegeneration in ATM mutants. Three lines of evidence indicate that ATM mutations cause neurodegeneration by activating the Nuclear Factor-κB (NF-κB) transcription factor Relish, a key regulator of the Immune deficiency (Imd) IIR signaling pathway. First, the level of upregulation of IIR genes, including Relish target genes, was directly correlated with the level of neurodegeneration in ATM mutants. Second, Relish mutations inhibited upregulation of IIR genes and neurodegeneration in ATM mutants. Third, overexpression of constitutively active Relish in glial cells activated the IIR and caused neurodegeneration. In contrast, we found that Imd and Dif mutations did not affect neurodegeneration in ATM mutants. Imd encodes an activator of Relish in the response to gram-negative bacteria, and Dif encodes an immune responsive NF-κB transcription factor in the Toll signaling pathway. These data indicate that the signal that causes neurodegeneration in ATM mutants activates a specific NF-κB protein and does so through an unknown activator. In summary, these findings suggest that neurodegeneration in human A-T is caused by activation of a specific NF-κB protein in glial cells.
MeSH Terms
- Animals
- Ataxia Telangiectasia
- Ataxia Telangiectasia Mutated Proteins
- Brain
- Cell Cycle Proteins
- Cell Death
- DNA-Binding Proteins
- Disease Models, Animal
- Drosophila Proteins
- Drosophila melanogaster
- Gene Expression Regulation
- Humans
- Immunity, Innate
- Longevity
- Motor Activity
- Mutation
- Nerve Degeneration
- Neuroglia
- Protein-Serine-Threonine Kinases
- Transcription Factors
- Tumor Suppressor Proteins
The underlying mechanism behind age-induced wastage of the human ovarian follicle reserve is unknown. We identify impaired ATM (ataxia-telangiectasia mutated)-mediated DNA double-strand break (DSB) repair as a cause of aging in mouse and human oocytes. We show that DSBs accumulate in primordial follicles with age. In parallel, expression of key DNA DSB repair genes BRCA1, MRE11, Rad51, and ATM, but not BRCA2, declines in single mouse and human oocytes. In Brca1-deficient mice, reproductive capacity was impaired, primordial follicle counts were lower, and DSBs were increased in remaining follicles with age relative to wild-type mice. Furthermore, oocyte-specific knockdown of Brca1, MRE11, Rad51, and ATM expression increased DSBs and reduced survival, whereas Brca1 overexpression enhanced both parameters. Likewise, ovarian reserve was impaired in young women with germline BRCA1 mutations compared to controls as determined by serum concentrations of anti-Müllerian hormone. These data implicate DNA DSB repair efficiency as an important determinant of oocyte aging in women.
MeSH Terms
- Adolescent
- Adult
- Age Factors
- Aging
- Animals
- Anti-Mullerian Hormone
- BRCA1 Protein
- BRCA2 Protein
- Cellular Senescence
- Child
- Child, Preschool
- DNA Breaks, Double-Stranded
- DNA Repair
- Female
- Fertility
- Gene Expression Regulation
- Humans
- Mice
- Mice, Transgenic
- Mutation
- Oocytes
- Ovary
- RNA Interference
- Young Adult