AGO2 silences mobile transposons in the nucleus of quiescent cells [ChIP-seq]
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ABSTRACT:
ORGANISM(S): Mus
PROVIDER: GSE203047 | GEO | 2022/07/18
REPOSITORIES: GEO
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Project description:Argonaute 2 (AGO2) is a cytoplasmic component of the miRNA pathway with essential roles in development and disease. Yet, little is known about its regulation in vivo. Here, we show that in mouse quiescent cells, AGO2 localizes almost exclusively to the nucleus. In quiescent splenocytes, AGO2’s subcellular localization is modulated by the Pi3K-AKT-mTOR pathway, a well-established regulator of quiescence. Signaling through this pathway in proliferating cells promotes AGO2 cytoplasmic accumulation at least in part by stimulating the expression of TNRC6, an AGO2 binding partner in the miRNA pathway. In contrast, low signaling in quiescent cells enables AGO2 to accumulate in the nucleus where it binds to young mobile transposons co-transcriptionally. Loss of AGO2 in quiescent cells results in upregulation of transposon transcripts suggesting it performs functions analogous to those of PIWI in the germline. Our results point to an essential but previously unrecognized nuclear role for AGO2 during mammalian quiescence as part of a genome-defense system against transposable elements.
2022-07-18 | GSE203048 | GEO
Project description:Argonaute 2 (AGO2) is a cytoplasmic component of the miRNA pathway with essential roles in development and disease. Yet, little is known about its regulation in vivo. Here, we show that in mouse quiescent cells, AGO2 localizes almost exclusively to the nucleus. In quiescent splenocytes, AGO2’s subcellular localization is modulated by the Pi3K-AKT-mTOR pathway, a well-established regulator of quiescence. Signaling through this pathway in proliferating cells promotes AGO2 cytoplasmic accumulation at least in part by stimulating the expression of TNRC6, an AGO2 binding partner in the miRNA pathway. In contrast, low signaling in quiescent cells enables AGO2 to accumulate in the nucleus where it binds to young mobile transposons co-transcriptionally. Loss of AGO2 in quiescent cells results in upregulation of transposon transcripts suggesting it performs functions analogous to those of PIWI in the germline. Our results point to an essential but previously unrecognized nuclear role for AGO2 during mammalian quiescence as part of a genome-defense system against transposable elements.
2022-07-22 | GSE208572 | GEO
Project description:The liver-specific microRNA, miR-122, is an essential host factor for replication of hepatitis C virus (HCV), an important infectious cause of chronic liver disease and hepatocellular carcinoma. miR-122 stabilizes the positive-strand HCV RNA genome and promotes viral RNA synthesis by binding two closely spaced sites (S1 and S2) near the 5’ end of the genome in association with Ago2. Ago2 is essential for both host factor activities, but whether other host proteins are involved is unknown. Using a quantitative proteomics approach, we identified TNRC6A (GW182) and its paralogs (TNRC6B and TNRC6C), as functionally important components of the miR-122/Ago2 host factor complex binding HCV RNA. Depletion of any two TNRC6 proteins reduced HCV replication in Huh-7.5 cells,but did not reduce viral RNA stability or translational activity, but rather dampened miR-122 stimulation of viral RNA synthesis. However, TNRC6 depletion had no effect on replication of HCV in which S2 was mutated so that miR-122 binds only S1, whereas it significantly enhanced replication when S1 was mutated and only S2 bound by miR-122. Consistent with this, we found that TNRC6 proteins preferentially associate with the S1 site, and that the association of Ago2 with S2 is increased in TNRC6-depleted cells. Collectively, these data suggest a model in which TNRC6 proteins, which are known to interact with Ago2, preferentially direct the miR-122/Ago2 complex to S1 while restricting its association with S2, thereby fine tuning the spatial organization of miR-122/Ago2 complexes bound to the viral RNA.
2019-04-24 | PXD013054 | Pride
Project description:Argonaute 2 (AGO2), the catalytic engine of RNAi, is typically associated with inhibition of translation in the cytoplasm. Contrary to dogma, AGO2 has also been implicated in nuclear processes including transcription and splicing. There has been little insight into AGO2's nuclear interactions or how they might differ relative to cytoplasm. Here we investigate the interactions of cytoplasmic and nuclear AGO2 using semi-quantitative mass spectrometry. Mass spectrometry often reveals long lists of candidate proteins, complicating efforts to rigorously discriminate true interacting partners from artifacts. We prioritized candidates using orthogonal analytical strategies that compare replicate mass spectra of proteins associated with FLAG-tagged and endogenous AGO2. Interactions with TRNC6A, TRNC6B, TNRC6C, and AGO3 are conserved between nuclei and cytoplasm. TAR binding protein interacted stably with cytoplasmic AGO2 but not nuclear AGO2, consistent with strand loading in the cytoplasm. Our data suggest that the core RNAi machinery is conserved between the nucleus and cytoplasm but that accessory proteins differ. Orthogonal analysis of mass spectra is a powerful approach to streamlining identification of protein partners.
2016-02-11 | MSV000079508 | MassIVE
Project description:A majority of metazoan mRNAs are under microRNA (miRNA)/Argonaute (Ago)-mediated control of RNA stability at the post-transcriptional level. Although the molecular mechanism of the miRNA-mediated repression of target mRNAs through Ago/TNRC6 pathway have been largely elucidated, however, the existence of alternative TNRC6-independent miRNA-mediated post-transcriptional gene regulation pathway remains unknown. Here, we suggest that endogenous miRNAs (endo-miRNAs) can downregulate the target mRNAs via the alternative molecular pathway, Ago-associated UPF1/SMG7, core mediators of nonsense-mediated mRNA decay. Global analyses of mRNAs in a response to UPF1 RNA interference in miRNA-deficient cells reveal that 3’UTR-length-dependent mRNA decay by UPF1 requires endo-miRNA targeting via CUG motif. The repression of miRNA targets is more additively or synergistically accomplished by combination of Ago2 and UPF1 through UPF1-associated SMG7, recruiting CCR4-NOT deadenylase complex, in TNRC6-independent manner. We expect that the new miRNA-mediated mRNA decay pathway enables the miRNA targeting to become more predictable and expand the miRNA-mRNA regulatory network.
2019-06-30 | GSE99169 | GEO
Project description:Background: Although quiescence—reversible cell-cycle arrest—is a key part in the life history and fate of many mammalian cell types, the mechanisms of gene regulation in quiescent cells are poorly understood. We sought to clarify the role of microRNAs as regulators of the cellular functions of quiescent human fibroblasts. Results: Using microarrays, we discovered that the expression of the majority of profiled microRNAs differed between proliferating and quiescent fibroblasts. Fibroblasts induced into quiescence by contact inhibition or serum starvation had similar microRNA profiles, indicating common changes induced by distinct quiescence signals. By analyzing the gene expression patterns of microRNA target genes with quiescence, we discovered a strong regulatory function for miR-29, which is downregulated with quiescence. Using microarrays and immunoblotting, we confirmed that miR-29 targets genes encoding collagen and other extracellular matrix proteins and that those target genes are induced in quiescence. In addition, overexpression of miR-29 resulted in more rapid cell cycle re-entry from quiescence. We also found that let-7 and miR-125 were upregulated in quiescent cells. Overexpression of either one alone resulted in slower cell cycle re-entry from quiescence, while the combination of both together slowed cell cycle re-entry even further. Conclusions: microRNAs regulate key aspects of fibroblast quiescence including the proliferative state of the cells as well as their gene expression profiles, in particular, the induction of extracellular matrix proteins in quiescent fibroblasts. microRNAs in human neonatal dermal fibroblasts in 3 cell cycle conditions (proliferating, 4 days serum starved, 7 days contact inhibited) were analyzed by one color microarray. 3 separate fibroblast cell lines from different human donors were analyzed for each condition, with two separate labeling and hybridization samples for each cell line. In total, 18 samples were hybridized to the microRNA microarray.
2012-12-05 | E-GEOD-42593 | biostudies-arrayexpress
Project description:Background: Although quiescence—reversible cell-cycle arrest—is a key part in the life history and fate of many mammalian cell types, the mechanisms of gene regulation in quiescent cells are poorly understood. We sought to clarify the role of microRNAs as regulators of the cellular functions of quiescent human fibroblasts. Results: Using microarrays, we discovered that the expression of the majority of profiled microRNAs differed between proliferating and quiescent fibroblasts. Fibroblasts induced into quiescence by contact inhibition or serum starvation had similar microRNA profiles, indicating common changes induced by distinct quiescence signals. By analyzing the gene expression patterns of microRNA target genes with quiescence, we discovered a strong regulatory function for miR-29, which is downregulated with quiescence. Using microarrays and immunoblotting, we confirmed that miR-29 targets genes encoding collagen and other extracellular matrix proteins and that those target genes are induced in quiescence. In addition, overexpression of miR-29 resulted in more rapid cell cycle re-entry from quiescence. We also found that let-7 and miR-125 were upregulated in quiescent cells. Overexpression of either one alone resulted in slower cell cycle re-entry from quiescence, while the combination of both together slowed cell cycle re-entry even further. Conclusions: microRNAs regulate key aspects of fibroblast quiescence including the proliferative state of the cells as well as their gene expression profiles, in particular, the induction of extracellular matrix proteins in quiescent fibroblasts. mRNAs were analyzed by two color microarray from three separate human neonatal dermal fibroblasts cell lines transfected either with a miR-29b mimic or a control short dsRNA. One sample was labeled and analyzed in duplicate to ensure consistency in labeling and hybridization technique.
2012-12-05 | E-GEOD-42613 | biostudies-arrayexpress
Project description:Argonaute 2 (AGO2) is a ubiquitously expressed protein critical for regulation of mRNA translation and vital to animal development. AGO2 protein is found in both cytoplasmic and nuclear compartments, and while its cytoplasmic role is well studied, the biological relevance of nuclear AGO2 is unclear. Here, we address this problem in vivo, using developing spermatogenic cells as a model. We find that AGO2 transiently binds both chromatin and nucleus-specific mRNA transcripts of hundreds of genes required for sperm production during male meiosis in mice, and that germline conditional knockout (cKO) of Ago2 causes depletion of the encoded proteins. Correspondingly, Ago2 cKO males exhibit abnormal sperm head morphology and reduced sperm count, along with reduced postnatal viability of offspring. Together, our data reveal an unexpected nuclear role for AGO2 in enhancing expression of developmentally important genes during mammalian male reproduction.
2022-07-19 | GSE181264 | GEO
Project description:Many cells in mammals exist in the state of quiescence, which is characterized by reversible exit from the cell cycle. Quiescent cells are widely reported to exhibit reduced size, nucleotide synthesis, and metabolic activity. Much lower glycolytic rates have been reported in quiescent compared with proliferating lymphocytes. In contrast, we show here that primary human fibroblasts continue to exhibit high metabolic rates when induced into quiescence via contact inhibition. By monitoring isotope labeling through metabolic pathways and quantitatively identifying fluxes from the data, we show that contact-inhibited fibroblasts utilize glucose in all branches of central carbon metabolism at rates similar to those of proliferating cells, with greater overflow flux from the pentose phosphate pathway back to glycolysis. Inhibition of the pentose phosphate pathway resulted in apoptosis preferentially in quiescent fibroblasts. By feeding the cells labeled glutamine, we also detected a “backwards” flux in the tricarboxylic acid cycle from α-ketoglutarate to citrate that was enhanced in contact-inhibited fibroblasts; this flux likely contributes to shuttling of NADPH from the mitochondrion to cytosol for redox defense or fatty acid synthesis. The high metabolic activity of the fibroblasts was directed in part toward breakdown and resynthesis of protein and lipid, and in part toward excretion of extracellular matrix proteins. Thus, reduced metabolic activity is not a hallmark of the quiescent state. Quiescent fibroblasts, relieved of the biosynthetic requirements associated with generating progeny, direct their metabolic activity to preservation of self integrity and alternative functions beneficial to the organism as a whole. mRNAs were analyzed by two color microarray from two separate human neonatal dermal fibroblasts cell lines in proliferating, 7 days contact inhibition, or 14 days contact inhibition. Contact inhibited samples were co-hybridized to proliferating samples as a control, while an additional array co-hybridized the two proliferating samples to analyze reproducibility.
2012-11-30 | E-GEOD-42612 | biostudies-arrayexpress
Project description:Transition from proliferation to quiescence brings about extensive changes in cellular behavior and structure. However, genes critical for establishing and/or for maintaining quiescence are largely unknown. The fission yeast S. pombe is found as an excellent model for studying this problem, because it becomes quiescent under nitrogen starvation. Here we characterize 610 temperature-sensitive (ts) mutants, and identify 33 genes required for entry into and the maintenance of quiescence. These genes cover a broad range of cellular functions in the cytoplasm, membrane and the nucleus, encoding proteins for stress-responsive and cell cycle kinase signaling pathway, actin-bound and osmo-controlling endosome formation, RNA transcription, splicing and ribosome biogenesis, chromatin silencing, biosynthesis of lipid and ATP, cell wall and membrane morphogenesis, protein trafficking and vesicle fusion. We specifically highlight Fcp1, CTD phosphatase of RNA polymerase II, which differentially affects transcription of genes involved in quiescence and proliferation. We propose that the transcriptional role of Fcp1 is central to differentiate quiescence from proliferation. Experiment Overall Design: Gene expression profile under nitrogen rich or starved condition at 26ºC or 37ºC in WT (L972) or fcp1-452 ts mutant strain of fission yeast.
2009-05-11 | E-GEOD-14319 | biostudies-arrayexpress