DICER1
Endoribonuclease Dicer (EC 3.1.26.3) (Helicase with RNase motif) (Helicase MOI) [DICER] [HERNA] [KIAA0928]
PublicationsПравить
Loss-of-function or knockout mouse models have established a fundamental role for the RNAse III enzyme DICER1 in development and tissue morphogenesis and/or homeostasis. These functions are currently assumed to result mainly from the DICER1-dependent biogenesis of microRNAs which exhibit important gene expression regulatory properties. However, non-canonical DICER1 functions have recently emerged. These include interaction with the DNA damage response (DDR) pathway and the processing of cytotoxic non-coding RNAs, suggesting that DICER1 might also participate in the regulation of major cellular processes through miRNA-independent mechanisms. Recent findings indicated that reduced [i]Dicer1[/i] expression, which correlates with worsened symptoms in mouse models of joint inflammation, is also noted in fibroblast-like synoviocytes (FLS) harvested from rheumatoid arthritis (RA) patients, as opposed to FLS cultured from biopsies of osteoarthritic patients. In addition, low DICER1 levels are associated with the establishment of cellular stress and its associated responses, such as cellular senescence. Senescent and/or stressed cells are associated with an inflammatory secretome (cytokines and chemokines), as well as with "find-me" and "eat-me" signals which will attract and activate the innate immune compartment (NK cells, macrophages, and neutrophils) to be eliminated. Failure of this immunosurveillance mechanism and improper restauration of homeostasis could lead to the establishment of a systemic and chronic inflammatory state. In this review, we suggest that reduced DICER1 expression contributes to a vicious cycle during which accumulating inflammation and premature senescence, combined to inadequate innate immunity responses, creates the appropriate conditions for the initiation and/or progression of autoimmune-autoinflammatory diseases, such as RA.
Keywords
- Dicer1
- ageing
- inflammation
- rheumatoid arthritis
- senescence
Gene expression is dynamically regulated in a variety of mammalian physiologies. During mammalian aging, there are changes that occur in protein expression that are highly controlled by the regulatory steps in transcription, post-transcription, and post-translation. Although there are global profiles of human transcripts during the aging processes available, the mechanism(s) by which transcripts are differentially expressed between young and old cohorts remains unclear. Here, we report on N6-methyladenosine (m6A) RNA modification profiles of human peripheral blood mononuclear cells (PBMCs) from young and old cohorts. An m6A RNA profile identified a decrease in overall RNA methylation during the aging process as well as the predominant modification on proteincoding mRNAs. The m6A-modified transcripts tend to be more highly expressed than nonmodified ones. Among the many methylated mRNAs, those of DROSHA and AGO2 were heavily methylated in young PBMCs which coincided with a decreased steady-state level of AGO2 mRNA in the old PBMC cohort. Similarly, downregulation of AGO2 in proliferating human diploid fibroblasts (HDFs) also correlated with a decrease in AGO2 mRNA modifications and steady-state levels. In addition, the overexpression of RNA methyltransferases stabilized AGO2 mRNA but not DROSHA and DICER1 mRNA in HDFs. Moreover, the abundance of miRNAs also changed in the young and old PBMCs which are possibly due to a correlation with AGO2 expression as observed in AGO2-depleted HDFs. Taken together, we uncovered the role of mRNA methylation on the abundance of AGO2 mRNA resulting in the repression of miRNA expression during the process of human aging.
MeSH Terms
- Adult
- Aging
- Argonaute Proteins
- Cells, Cultured
- Down-Regulation
- Gene Expression
- Humans
- Male
- Methylation
- Methyltransferases
- Middle Aged
- RNA
- RNA Stability
Keywords
- aging
- m6A RNA methylation
- post transcriptional gene regulation
Metformin, an oral hypoglycemic agent, has been used for decades to treat type 2 diabetes mellitus. Recent studies indicate that mice treated with metformin live longer and have fewer manifestations of age-related chronic disease. However, the molecular mechanisms underlying this phenotype are unknown. Here, we show that metformin treatment increases the levels of the microRNA-processing protein DICER1 in mice and in humans with diabetes mellitus. Our results indicate that metformin upregulates DICER1 through a post-transcriptional mechanism involving the RNA-binding protein AUF1. Treatment with metformin altered the subcellular localization of AUF1, disrupting its interaction with DICER1 mRNA and rendering DICER1 mRNA stable, allowing DICER1 to accumulate. Consistent with the role of DICER1 in the biogenesis of microRNAs, we found differential patterns of microRNA expression in mice treated with metformin or caloric restriction, two proven life-extending interventions. Interestingly, several microRNAs previously associated with senescence and aging, including miR-20a, miR-34a, miR-130a, miR-106b, miR-125, and let-7c, were found elevated. In agreement with these findings, treatment with metformin decreased cellular senescence in several senescence models in a DICER1-dependent manner. Metformin lowered p16 and p21 protein levels and the abundance of inflammatory cytokines and oncogenes that are hallmarks of the senescence-associated secretory phenotype (SASP). These data lead us to hypothesize that changes in DICER1 levels may be important for organismal aging and to propose that interventions that upregulate DICER1 expression (e.g., metformin) may offer new pharmacotherapeutic approaches for age-related disease.
MeSH Terms
- Adult
- Aging
- Animals
- Caloric Restriction
- Cell Line
- Cell Nucleus
- Cellular Senescence
- DEAD-box RNA Helicases
- Demography
- Female
- Gene Expression Regulation
- Heterogeneous Nuclear Ribonucleoprotein D0
- Heterogeneous-Nuclear Ribonucleoprotein D
- Humans
- Male
- Metformin
- Mice
- MicroRNAs
- Middle Aged
- Phenotype
- Protein Transport
- RNA, Messenger
- Ribonuclease III
Keywords
- AUF1
- RNA-binding proteins
- aging
- caloric restriction
- diabetes mellitus
- microRNA
The purpose of this study was to compare the risks of radiation in screening strategies using chest radiographs and CT to detect a rare cancer in a genetically predisposed population against the risks of undetected disease. A decision analytic model of diagnostic imaging screening strategies was built to predict outcomes and cumulative radiation doses for children with DICER1 mutations screened for pleuropulmonary blastoma. Screening strategies compared were chest radiographs followed by chest CT for a positive radiographic result and CT alone. Screening frequencies ranged from once in 3 years to once every 3 months. BEIR VII (model VII proposed by the Committee on the Biological Effects of Ionizing Radiation) risk tables were used to predict excess cancer mortality for each strategy, and the corresponding loss of life expectancy was calculated using Surveillance Epidemiologic and End Results (SEER) statistics. Loss of life expectancy owing to undetected progressive pleuropulmonary blastoma was estimated on the basis of data from the International Pleuropulmonary Blastoma Registry. Sensitivity analysis was performed for all model parameters. Loss of life expectancy owing to undetected disease in an unscreened population exceeded that owing to radiation-induced cancer for all screening scenarios investigated. Increases in imaging frequency decreased loss of life expectancy for the combined (chest radiographs and CT) screening strategy but increased that for the CT-only strategy. This was because loss of life expectancy for combined screening is dominated by undetected disease, whereas loss of life expectancy for CT screening is dominated by radiation-induced cancers. Even for a rare disease such as pleuropulmonary blastoma, radiographic screening of infants and young children with cancer-predisposing mutations may result in improved life expectancy compared with the unscreened population. The benefit of screening will be greater for diseases with a higher screening yield.
MeSH Terms
- Child, Preschool
- DEAD-box RNA Helicases
- Decision Support Techniques
- Female
- Genetic Predisposition to Disease
- Humans
- Infant
- Life Expectancy
- Lung Neoplasms
- Male
- Mutation
- Neoplasms, Radiation-Induced
- Pulmonary Blastoma
- Radiation Dosage
- Radiography, Thoracic
- Ribonuclease III
- Risk
- Sensitivity and Specificity
- Tomography, X-Ray Computed
Keywords
- CT
- chest radiograph
- radiation risk
- rare diseases
- screening
In order to better understand the mechanisms governing the display of mast cell characteristics in human mast cells (MCs), such as cord blood (CB)-derived cultured mast cells, peripheral blood (PB)-derived cultured MCs, and differentiated adult-lung cultured MCs, we examined the transcriptomes of these three types MCs using oligonucleotide microarray (GeneChip) and hierarchical clustering analysis. The expression profile of CB-derived MCs substantially differed from those of PB- and lung-derived MCs. In CB-derived MCs, we identified 132 up-regulated transcripts, such as MARCKS, KRT1, TIMP2, SERPINA1, and TLR2, and 428 down-regulated transcripts, such as LTBP3, CDC42BPA, DDO, DICER1, and FCER1A. Moreover, using RT-PCR and FACS analysis, we confirmed the expression of TLR2, which plays an important role in innate immunity, in CB-derived MCs but not in PB-derived MCs. In addition, it was observed that CB-derived MCs uniquely release histamine and CCL1, which are produced by human MCs but not by human monocytes, in response to peptidoglycan (PGN), although it had been controversy issue whether CB-derived MCs could, in fact, induce degranulation in response to PGN. These results indicated that in innate immunity MCs derived from neonatal hemopoietic cells might have unique functions compared to their adult counterparts because of different gene profiles.
MeSH Terms
- Adult
- Aging
- Cell Differentiation
- Cluster Analysis
- Down-Regulation
- Fetal Blood
- Gene Expression Profiling
- Histamine Release
- Humans
- Mast Cells
- Membrane Glycoproteins
- Oligonucleotide Array Sequence Analysis
- RNA, Messenger
- Receptors, Cell Surface
- Stem Cells
- Toll-Like Receptor 2
- Toll-Like Receptors
- Transcription, Genetic
- Up-Regulation