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Loss of Lamin A leads to nuclear translocation of AGO2 mediated by EGFR signaling and inactivation of RNAi

ABSTRACT: In mammals, RNA interference (RNAi) is mostly studied as a cytoplasmic event, however, numerous reports convincingly showed nuclear localization of AGO proteins. Nevertheless, the mechanism of the nuclear entry remains to be fully elucidated, and the extent of nuclear RNAi explored. The nuclear import of large proteins requires active transport through the nuclear envelope (NE). Therefore, we hypothesized that the NE, and its composition, is important for nuclear AGO2 translocation. Lamin A knockout significantly induced nuclear influx of AGO2 in SHSY5Y neuroblastoma and A375 melanoma cancer cells. We unravelled that the loss of Lamin A leads to EGFR and Src kinase activation, which regulates the turnover and stability of cytoplasmic specifically AGO2. Furthermore, EGFR mediated phosphorylation at Y393 inhibits the activity of nuclear RNAi. This was evident by AGO fPAR-CLIP in WT and KO cells, where we observed a decrease in RNAi potential. Mass spectrometry of AGO interactome, from the nuclear fraction, indicated that AGO2 is in complex with FAM120A, which may further reduced the activity of RNAi by competing with AGO2 transcript binding. Therefore, loss of Lamin A starts a signalling cascade that mediates nuclear AGO2 translocation to rapidly inhibit RNAi.

ORGANISM(S): Homo sapiens

PROVIDER: GSE235156 | GEO | 2023/06/22

REPOSITORIES: GEO

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Loss of Lamin A leads to nuclear translocation of AGO2 mediated by EGFR signaling and inactivation of RNAi

Project description:In mammals, RNA interference (RNAi) is mostly studied as a cytoplasmic event, however, numerous reports convincingly showed nuclear localization of AGO proteins. Nevertheless, the mechanism of the nuclear entry remains to be fully elucidated, and the extent of nuclear RNAi explored. The nuclear import of large proteins requires active transport through the nuclear envelope (NE). Therefore, we hypothesized that the NE, and its composition, is important for nuclear AGO2 translocation. Lamin A knockout significantly induced nuclear influx of AGO2 in SHSY5Y neuroblastoma and A375 melanoma cancer cells. We unravelled that the loss of Lamin A leads to EGFR and Src kinase activation, which regulates the turnover and stability of cytoplasmic specifically AGO2. Furthermore, EGFR mediated phosphorylation at Y393 inhibits the activity of nuclear RNAi. This was evident by AGO fPAR-CLIP in WT and KO cells, where we observed a decrease in RNAi potential. Mass spectrometry of AGO interactome, from the nuclear fraction, indicated that AGO2 is in complex with FAM120A, which may further reduced the activity of RNAi by competing with AGO2 transcript binding. Therefore, loss of Lamin A starts a signalling cascade that mediates nuclear AGO2 translocation to rapidly inhibit RNAi.

2023-06-20 | GSE235034 | GEO

Loss of Lamin A leads to the nuclear translocation of AGO2 and compromised RNA interference

Project description:In mammals, RNA interference (RNAi) was historically studied as a cytoplasmic event, however, in the last decade growing number of reports convincingly show nuclear localization of the AGO proteins. Nevertheless, the mechanism and the extent of nuclear RNAi remains to be fully elucidated. We found that reduced Lamin A levels significantly induced nuclear influx of AGO2 in SHSY5Y neuroblastoma and A375 melanoma cancer cell lines, which normally have no nuclear AGO2. Lamin A KO manifested a more pronounced effect in SHSY5Y cells compared to A375 evident by changes in cell morphology, increased cell proliferation and oncogenic miRNA expression. Furthermore, in SHSY5Y cells, AGO fPAR-CLIP in Lamin A KO cells revealed significantly reduced activity of RNAi. Further exploration of the nuclear AGO interactome by mass spectrometry indicated that AGO2 is in complex with FAM120A, an RNA binding protein and known interactor of AGO2. By performing FAM120A fPAR-CLIP we discovered that FAM120A co-binds AGO targets and that this competition reduces the activity of RNAi. Therefore, loss of Lamin A triggers nuclear AGO2 translocation, RNAi impairment and selective upregulation of oncogenic miRNAs to facilitate cancer cell proliferation.

2024-03-21 | GSE261593 | GEO

Loss of Lamin A leads to the nuclear translocation of AGO2 and compromised RNA interference

2024-03-21 | GSE261422 | GEO

The Core RNAi Machinery is Conserved Between the Cytoplasm and Nuclei of Human Cells

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

Argonaute proteins couple chromatin silencing to alternative splicing (RNA IP-Seq)

Project description:While Argonaute (AGO) proteins play a major role in transcriptional gene silencing (TGS) in many organisms, their role in the nucleus of somatic mammalian cells remains elusive. Here, we have purified AGO1 and AGO2 chromatin-embedded complexes, and found these proteins associated with previously described partners, but also with chromatin modifiers and, rather unexpectedly, with different splicing factors. Using the CD44 gene as a model for alternative splicing, we show that both AGO1 and AGO2 are required for Protein Kinase C (PKC)-dependent variant exon inclusion. AGO proteins facilitate the spliceosome recruitment and modulate the elongation rate of RNA polymerase II (RNAPII). The recruitment of AGO proteins to CD44 transcribed region is dependent on both the endonuclease Dicer and the chromodomain-containing protein HP1g, and results in locally increased levels of histone H3 lysine 9 (H3K9) methylation on variant exons. Genome wide analysis of splicing in either AGO2 or Dicer null cells showed that the two proteins have similar effects on many splicing events. Finally, sRNAs associated with nuclear AGO2 are mostly in sense orientation relative to protein-coding genes, supporting a role for intragenic antisense non-coding RNAs in the recruitment AGO and splicing factors. Together, our data demonstrate for the first time that the endogenous RNAi pathway is involved in alternative splicing decisions, unravelling a new model in which AGO proteins couple RNAPII elongation and chromatin modification. Deep sequencing of small RNAs (approx. 15-80 nucleotides) bound to either cytoplasmic or chromatin-associated AGO2 complex.

2012-09-10 | E-GEOD-39748 | biostudies-arrayexpress

Sites for Argonaute Binding within Human Nuclear RNA and their Impact on Alternative Splicing

Project description:Mammalian RNA interference (RNAi) is often linked to regulation in the cytoplasm. While synthetic RNAs regulate transcription and splicing, endogenous functions for nuclear RNAi have been obscure. Using enhanced crosslinking immunoprecipitation (eCLIP), we mapped AGO2 binding sites within nuclear RNA. The strongest AGO binding sites mapped to miRNAs. The prevalence of individual miRNAs was similar in the cytoplasm and the nucleus. Most statistically-significant AGO2 binding was within intron boundaries. RNAseq comparing AGO1, AGO2, AGO1/2, and AGO1/2/3 knockout to wild-type cells revealed that binding was associated with both up- and down-regulation of gene expression. We observed changes of splicing at genes with significant AGO binding at exon/intron junctions or within introns. Splicing changes were confirmed by RT-PCR and could be recapitulated by synthetic duplex RNAs that target the sites of AGO binding. Inhibition of miRNA action by addition of an anti-miR reversed miRNA-mediated control of splicing. We conclude: 1) That AGO binding sites occur throughout nuclear RNA but are often within introns; 2) The distribution of miRNAs is similar in the nucleus and cytoplasm; and 3) miRNAs can control gene splicing. Nuclear RNAi has the potential to be a natural regulatory mechanism but careful study will be necessary to identify critical RNA drivers of normal physiology and disease.

2021-02-10 | GSE161559 | GEO

A nuclear role for the Argonaute protein AGO2 in mammalian gametogenesis

Project description:The reduced sperm count observed in Ago2 cKO mice implies that AGO2 has non-redundant functions in the male germ line. Because AGO2 is a key protein in the RNA interference (RNAi) pathway, we first postulated that AGO2 loss disrupts normal transcriptional and translational dynamics of target mRNAs relevant to sperm maturation. To address this hypothesis, we took advantage of the apparently normal spermatogenesis in Ago2 cKO mice, which allowed us to purify matched meiotic and post-meiotic germ cells from Ago2 cKO and wild type controls. We examined changes in the transcriptome and proteome of these two spermatogenic stages in Ago2 cKO relative to control mice using RNA-seq and quantitative mass spectrometry (MS). To further examine if the changes in mRNA and protein levels detected in Ago2 cKO germ cells was due to a loss of regulation by the canonical AGO2-miRNA pathway, we characterized AGO2 protein interactors by AGO2 immunoprecipitation-mass spectrometry (IP-MS) in cytoplasmic and nuclear fractions of post-meiotic cells

2022-08-01 | PXD027935 | Pride

Argonaute proteins couple chromatin silencing to alternative splicing (exon array)

Project description:While Argonaute (AGO) proteins play a major role in transcriptional gene silencing (TGS) in many organisms, their role in the nucleus of somatic mammalian cells remains elusive. Here, we have purified AGO1 and AGO2 chromatin-embedded complexes, and found these proteins associated with previously described partners, but also with chromatin modifiers and, rather unexpectedly, with different splicing factors. Using the CD44 gene as a model for alternative splicing, we show that both AGO1 and AGO2 are required for Protein Kinase C (PKC)-dependent variant exon inclusion. AGO proteins facilitate the spliceosome recruitment and modulate the elongation rate of RNA polymerase II (RNAPII). The recruitment of AGO proteins to CD44 transcribed region is dependent on both the endonuclease Dicer and the chromodomain-containing protein HP1g, and results in locally increased levels of histone H3 lysine 9 (H3K9) methylation on variant exons. Genome wide analysis of splicing in either AGO2 or Dicer null cells showed that the two proteins have similar effects on many splicing events. Finally, sRNAs associated with nuclear AGO2 are mostly in sense orientation relative to protein-coding genes, supporting a role for intragenic antisense non-coding RNAs in the recruitment AGO and splicing factors. Together, our data demonstrate for the first time that the endogenous RNAi pathway is involved in alternative splicing decisions, unravelling a new model in which AGO proteins couple RNAPII elongation and chromatin modification. Study of AGO2 or Dicer knock-out on gene expression and splicing regulation in MEF cells Transcriptome analysis of AGO2 and Dicer null MEF cells on GeneChipM-BM-. Mouse Exon 1.0 ST Arrays (Affymetrix). Dicer null MEF cells and wild-type MEF cells were from M. Otsuka. AGO2 null MEF cells were from A. Tarakhovsky. Experiment has been done in experimental triplicates. 9 Total samples were analyzed.

2012-09-10 | E-GEOD-39746 | biostudies-arrayexpress

Analysis of Ago2-associated transcripts after knockdown of Importin8

Project description:Small regulatory RNAs including small interfering RNAs (siRNAs) and microRNAs (miRNAs) guide Argonaute (Ago) proteins to specific target RNAs leading to mRNA destabilization or translational repression. We recently reported the identification of Importin 8 (Imp8) as a novel component of miRNA-guided regulatory pathways. Imp8 interacts with Ago proteins and localizes to cytoplasmic processing bodies (P-bodies), structures involved in RNA metabolism. For this micro-array dataset, we used immunoprecipitations of Ago2-associated mRNAs followed by micro-array analysis. The results demonstrate that Imp8 is required for recruiting Ago protein complexes to a large set of Ago2-associated target mRNAs allowing for efficient and specific gene silencing. Therefore, we provide evidence that Imp8 is required for cytoplasmic miRNA-guided gene silencing.

2009-01-22 | GSE14054 | GEO

Argonaute proteins couple chromatin silencing to alternative splicing (exon array)

Project description:While Argonaute (AGO) proteins play a major role in transcriptional gene silencing (TGS) in many organisms, their role in the nucleus of somatic mammalian cells remains elusive. Here, we have purified AGO1 and AGO2 chromatin-embedded complexes, and found these proteins associated with previously described partners, but also with chromatin modifiers and, rather unexpectedly, with different splicing factors. Using the CD44 gene as a model for alternative splicing, we show that both AGO1 and AGO2 are required for Protein Kinase C (PKC)-dependent variant exon inclusion. AGO proteins facilitate the spliceosome recruitment and modulate the elongation rate of RNA polymerase II (RNAPII). The recruitment of AGO proteins to CD44 transcribed region is dependent on both the endonuclease Dicer and the chromodomain-containing protein HP1g, and results in locally increased levels of histone H3 lysine 9 (H3K9) methylation on variant exons. Genome wide analysis of splicing in either AGO2 or Dicer null cells showed that the two proteins have similar effects on many splicing events. Finally, sRNAs associated with nuclear AGO2 are mostly in sense orientation relative to protein-coding genes, supporting a role for intragenic antisense non-coding RNAs in the recruitment AGO and splicing factors. Together, our data demonstrate for the first time that the endogenous RNAi pathway is involved in alternative splicing decisions, unravelling a new model in which AGO proteins couple RNAPII elongation and chromatin modification. Study of AGO2 or Dicer knock-out on gene expression and splicing regulation in MEF cells

2012-09-10 | GSE39746 | GEO

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