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

ABSTRACT: 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

ORGANISM(S): Mus musculus

PROVIDER: GSE39746 | GEO | 2012/09/10

SECONDARY ACCESSION(S): PRJNA171691

REPOSITORIES: GEO

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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

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

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

2012-09-10 | GSE39748 | GEO

miRNAs associated with the different human Argonaute proteins

Project description:microRNAs (miRNAs) are small non-coding RNAs that function in literally all cellular processes. miRNAs interact with Argonaute (Ago) proteins and guide them to specific target sites located in the 3’ untranslated region (UTR) of target mRNAs leading to translational repression and deadenylation-induced mRNA degradation. Most miRNAs are processed from hairpin-structured precursors by the consecutive action of the RNase III enzymes Drosha and Dicer. However, processing of miR-451 is Dicer-independent and cleavage is mediated by the endonuclease Ago2. Here we have characterized miR-451 sequence and structure requirements for processing as well as sorting of miRNAs into different Ago proteins. Pre-miR-451 appears to be optimized for Ago2 cleavage and changes result in reduced processing. In addition, we show that the mature miR-451 only associates with Ago2 suggesting that mature miRNAs are not exchanged between different members of the Ago protein family. Based on cloning and deep sequencing of endogenous miRNAs associated with Ago1-3, we do not find evidence for miRNA sorting in human cells. However, Ago identity appears to influence the length of some miRNAs, while others remain unaffected. Examination of miRNAs associated with endogenous human Ago1-4 in HeLa cells

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A chromatin code for alternative splicing involving a putative association between CTCF and HP1α proteins

Project description:Alternative splicing is primarily controlled by the activity of splicing factors and by the elongation of the RNA polymerase II (RNAPII). Recent experiments have suggested a new complex network of splicing regulation involving chromatin, transcription and multiple protein factors. In particular, the CCCTC-binding factor (CTCF), the Argonaute protein AGO1, and members of heterochromatin protein 1 (HP1) family have been implicated in the regulation of splicing associated to chromatin and the elongation of RNAPII. These results raise the question of whether these proteins may associate at the chromatin level to modulate alternative splicing. RNA extraction from MCF-7 and MCF-10A cell lines. Splicing changes between these two cell lines were measured using a splice junction array (Affymetrix HJAY).

2015-05-04 | E-GEOD-38864 | biostudies-arrayexpress

miRNAs associated with the different human Argonaute proteins

2013-03-29 | GSE45506 | GEO

A chromatin code for alternative splicing involving a putative association between CTCF and HP1α proteins

2015-05-04 | GSE38864 | GEO

STUB1 regulates antiviral RNAi through inducing ubiquitination and degradation of Dicer and AGO2 in mammals

Project description:RNA interference (RNAi) is a cell-intrinsic antiviral defense conserved in diverse organisms. However, the mechanism by which mammalian antiviral RNAi is regulated is largely unknown. Herein, we uncover that STUB1, an E3 ubiquitin ligase, interacts with and ubiquitinates AGO2, the core component of RNAi pathway, resulting in the degradation of AGO2 via ubiquitin-proteasome system. Additionally, STUB1 can induce the degradation of the other mammalian AGO proteins including AGO1, AGO3, and AGO4. Our further study reveals that STUB1 also interacts with and mediates the ubiquitination of Dicer, the endoribonuclease responsible for siRNA or miRNA biogenesis, via K48-linked poly-ubiquitin, which induces the degradation of Dicer and its specialized form, termed antiviral Dicer (aviDicer) that usually expresses in stem cells. Loss of STUB1 upregulated Dicer and AGO2, thereby enhancing antiviral RNAi to effectively inhibit viral RNA replication in mammalian cells. In vivo, the STUB1 deficiency markedly enhanced the production of virus-derived siRNAs and elicited a potent antiviral effect against Enterovirus-A71 (EV-A71) infection in newborn mouse. Our findings demonstrate STUB1 as a novel negative regulator of RNAi by mediating the ubiquitination and degradation of Dicer and AGO proteins, and provide novel insights into the regulatory mechanism of antiviral RNAi in mammals.

2021-11-22 | GSE189203 | GEO

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

The dsRBP Staufen2 governs RNP assembly of neuronal Argonaute proteins

Project description:Here, we have characterized the role of the RNA-binding protein Staufen2, a potential Ago interactor, in RNP assembly. Staufen2 depletion resulted in the upregulation of Ago1/2 and the RISC effector proteins Ddx6 and Dcp1a. This upregulation was accompanied by the displacement of Ago2 from processing bodies, large RNPs implicated in RNA storage, and subsequent association of Ago2 with translating polysomes. Analysis of miRNA expression levels did not reveal changes of global miRNA abundance. In parallel, Staufen2 deficiency yielded decreased global translation. As the observed phenotype can be rescued by Ago1/2 knockdown, we propose a working model in which both Staufen2 and Ago proteins critically depend on each other and contribute to neuronal homeostasis.

2022-05-31 | GSE185935 | GEO

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