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R-loops induce repressive chromatin marks over mammalian gene terminators

ABSTRACT: The formation of R-loops is a natural consequence of the transcription process, caused by invasion of the DNA duplex by nascent transcripts. These structures have been considered rare transcriptional by-products with potential harmful effects on genome integrity, due to the fragility of the displaced DNA coding strand. However R-loops may also possess beneficial effects as their widespread formation has been detected over CpG island promoters in human genes. Furthermore we have previously shown that R-loops are particularly enriched over G-rich terminator elements. These facilitate RNA polymerase II (Pol II) pausing prior to efficient termination. Here we reveal an unanticipated link between R-loops and RNA interference (RNAi)-dependent H3K9me2 formation over pause site termination regions of mammalian protein coding genes. We show that R-loops induce antisense transcription over these pause elements which in turn lead to the generation of double-strand RNA (dsRNA) and recruitment of Dicer, Ago1, Ago2, and G9a histone lysine methyltransferase (HKMT). Consequently an H3K9me2 repressive mark is formed and Heterochromatin Protein 1γ (HP1γ) is recruited, that reinforces Pol II pausing prior to efficient transcriptional termination. We predict that R-loops promote a chromatin architecture that defines the termination region for a substantial subset of mammalian genes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE59878 | GEO | 2014/09/29

SECONDARY ACCESSION(S): PRJNA256971

REPOSITORIES: GEO

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R-loops induce repressive chromatin marks over mammalian gene terminators

Project description:The formation of R-loops is a natural consequence of the transcription process, caused by invasion of the DNA duplex by nascent transcripts. These structures have been considered rare transcriptional by-products with potential harmful effects on genome integrity, due to the fragility of the displaced DNA coding strand. However R-loops may also possess beneficial effects as their widespread formation has been detected over CpG island promoters in human genes. Furthermore we have previously shown that R-loops are particularly enriched over G-rich terminator elements. These facilitate RNA polymerase II (Pol II) pausing prior to efficient termination. Here we reveal an unanticipated link between R-loops and RNA interference (RNAi)-dependent H3K9me2 formation over pause site termination regions of mammalian protein coding genes. We show that R-loops induce antisense transcription over these pause elements which in turn lead to the generation of double-strand RNA (dsRNA) and recruitment of Dicer, Ago1, Ago2, and G9a histone lysine methyltransferase (HKMT). Consequently an H3K9me2 repressive mark is formed and Heterochromatin Protein 1γ (HP1γ) is recruited, that reinforces Pol II pausing prior to efficient transcriptional termination. We predict that R-loops promote a chromatin architecture that defines the termination region for a substantial subset of mammalian genes. PolIIS2ph ChIP-seq and input in untreated condition and treated with BIX and RNaseH1 overexpression in HeLa cells. The 4 samples have been multiplexed, pooled and sequenced on 3 lanes of Illumina HiSeq2000.

2014-09-29 | E-GEOD-59878 | biostudies-arrayexpress

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Project description:Paused RNA polymerase II that piles up near most human promoters is the target of mechanisms that control entry into productive elongation. Whether paused pol II is a stable or a dynamic target remains unresolved. We report that most 5’-paused pol II throughout the genome is turned over within 2 minutes. This process is revealed under hypertonic conditions that prevent pol II recruitment to promoters. This turnover requires cell viability but is not prevented by inhibiting transcription elongation suggesting that it is mediated at the level of termination. When initiation was prevented by triptolide during recovery from high salt, a novel pre-initiated state of pol II lacking the pausing factor Spt5 accumulated at transcription start sites. We propose that pol II occupancy near 5’ ends is governed by a cycle of ongoing assembly of pre-initiated complexes that transition to pause sites followed by eviction from the DNA template. This model suggests that mechanisms regulating the transition to productive elongation at pause sites operate on a dynamic population of pol II that is turning over at rates far higher than previously suspected. We suggest that a plausible alternative to elongation control via escape from a stable pause, is by escape from premature termination.

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The PNUTS phosphatase complex controls transcription pause release

Project description:Gene expression is regulated by controlling distinct steps of the transcriptional cycle, including initiation, pausing, elongation, and termination. Kinases phosphorylate RNA Polymerase II and associated factors to control transitions between these steps and act as central gene regulatory nodes. Similarly, phosphatases that dephosphorylate these components are emerging as important regulators of transcription, though their roles remain less well understood. Here we discover that the PNUTS-PP1 phosphatase complex plays an essential role in controlling transcription pause release in addition to its previously described function in transcription termination. Transcription pause release by the PNUTS complex is essential for almost all RNA Pol II-dependent gene transcription, relies on its PP1 phosphatase subunit, and controls the phosphorylation of factors required for pause release and elongation. Together, this reveals an essential new role for a phosphatase complex in transcription pause release and shows that the PNUTS complex is essential for RNA Poll II-dependent transcription.

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Coupling of co-transcriptional splicing and 3’ end Pol II pause during termination in Arabidopsis

Project description:In Arabidopsis, RNA Polymerase II (Pol II) often pauses within a few hundred base pairs downstream of the polyadenylation site, reflecting efficient transcriptional termination, but how such pause is regulated remains largely elusive. Here, we studied Pol II dynamics at gene 3’ end by combining comprehensive experiments with mathematical modelling. We generated high-resolution Ser2P Pol II positioning data specifically enriched at gene 3’ end and defined a 3’ end pause index (3’PI). The position but not the extent of the 3’ end pause correlates with termination window size. The 3’PI is not decreased but even mildly increased in the termination deficient mutant xrn3, indicating 3’ end pause is a regulatory step early during the termination and before XRN3 mediated RNA decay that releases the Pol II. Unexpectedly, 3’PI is closely associated with gene exon numbers and co-transcriptional splicing efficiency. Multiple exons genes often display stronger 3’ end pauses and more efficient on-chromatin splicing than genes with few exons. Chemical inhibition of splicing strongly reduces the 3’PI and disrupts its correlation with exon numbers but does not globally impact 3’ end readthrough levels. These results were further confirmed by fitting Pol II positioning data with a mathematical model, which enables the estimation of parameters that define Pol II dynamics. Our work highlights that the number of exons via co-transcriptional splicing is a major determinant of Pol II pausing levels at gene 3’ end in plants.

2023-05-27 | GSE205545 | GEO

Transcriptional Pause Sites Delineate Stable Nucleosome-Associated Premature Polyadenylation Suppressed by U1 snRNP [2P-seq]

Project description:Regulation of RNA polymerase II (Pol II) elongation is a critical step in gene regulation. Here, we report that U1 snRNP recognition and transcription pausing at stable nucleosomes are linked through premature polyadenylation signal (PAS) termination. By generating RNA exosome conditional deletion mouse embryonic stem cells, we identified a large class of polyadenylated short transcripts in the sense direction destabilized by the RNA exosome. These PAS termination events are enriched at the first few stable nucleosomes flanking CpG islands and suppressed by U1 snRNP. Thus, promoter-proximal Pol II pausing consists of two processes: TSS-proximal and +1 stable nucleosome pausing, with PAS termination coinciding with the latter. While pausing factors NELF/DSIF only function in the former step, flavopiridol-sensitive mechanism(s) and Myc modulate both steps. We propose that premature PAS termination near the nucleosome-associated pause site represents a common transcriptional elongation checkpoint regulated by U1 snRNP recognition, nucleosome stability, and Myc activity.

2018-02-01 | GSE100536 | GEO

Transcriptional Pause Sites Delineate Stable Nucleosome-Associated Premature Polyadenylation Suppressed by U1 snRNP [RNA-seq]

2018-02-01 | GSE100535 | GEO

Transcriptional Pause Sites Delineate Stable Nucleosome-Associated Premature Polyadenylation Suppressed by U1 snRNP [2P-seq, Pabpn1 CKO]

2018-02-01 | GSE107132 | GEO

PTEN modulates gene transcription by redistributing genome-wide RNA polymerase II occupancy [ChIP-seq]

Project description:Control of gene expression is one of the most complex yet continuous physiological processes impacting cellular homeostasis. RNA polymerase II (Pol II) transcription is tightly regulated at promoter-proximal regions by intricate dynamic processes including Pol II pausing, release into elongation, and premature termination. Here, we identify PTEN interacting with the Pol II transcription machinery and dephosphorylating Pol II C-terminal domain in vitro. PTEN alters the expression of hundreds of genes, and its restoration establishes Pol II promoter-proximal pausing in PTEN null cells. Furthermore, PTEN re-distributes genome-wide Pol II occupancy and possibly impacts Pol II pause duration, release, and elongation rate in order to enable precise gene regulation at genome-wide scale. Our observations demonstrate a direct and imperative role of PTEN in global transcriptional regulation.

2019-06-04 | GSE124657 | GEO

PTEN modulates gene transcription by redistributing genome-wide RNA polymerase II occupancy [RNA-seq]

2019-06-04 | GSE124658 | GEO

Stably-paused genes revealed through inhibition of transcription initiation by the TFIIH inhibitor Triptolide

Project description:Transcription by RNA Polymerase II (Pol II) in metazoan is regulated in several steps, including preinitiation complex (PIC) formation, initiation, Pol II escape, productive elongation, cotranscriptional RNA-processing and termination. Genome-wide studies have demonstrated that the phenomenon of promoter-bound Pol II pausing is widespread, especially for genes involved in developmental and stimulus-responsive pathways. However, a mechanistic understanding of the paused Pol II states at promoters is limited. For example, at a global level, it’s unclear to what extent the engaged paused Pol II is stably tethered to the promoter or undergoes rapid cycles of initiation and termination. Here we used the small molecule Triptolide (TPL), an XPB/TFIIH inhibitor, to block transcriptional initiation followed by measuring Pol II occupancy by ChIP-seq. This inhibition of initiation enables us to investigate different states of paused Pol II. Specifically, our global analysis reveals that most genes with paused Pol II, as defined by pausing index, show significant clearance of Pol II during the period of TPL treatment. Our study further identifies a group of genes with unexpectedly stably-paused Pol II, with unchanged Pol II occupancy even after one hour of inhibition of initiation. This group of genes constitutes a small portion of all paused genes defined by the conventional criterion of pausing index. These findings could pave the way for evaluating the contribution of different elongation/pausing factors on different states of Pol II pausing in developmental and other stimulus-responsive pathways. ChIP-Seq of total/Ser5P Pol II in HCT116 cells treated with DMSO or TPL in serum starvation/activation or normal conditions. Nascent RNA-seq in HCT116 cells treated with DMSO or TPL in starved condition.

2015-01-05 | E-GEOD-63314 | biostudies-arrayexpress

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