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In Vitro Transcription Recycling Assay Identifies PAF1 as a Driver of RNA Pol II Recycling

ABSTRACT: RNA Polymerase II transcriptional recycling is an underappreciated mechanism for which the required factors and contributions to overall gene expression levels are poorly understood. We describe an in vitro methodology facilitating unbiased identification of novel RNA Pol II transcriptional recycling factors and quantitative measurement of transcriptional output from recycled transcriptional components. Proof-of-principle experiments identified PAF1 complex components among recycling factors and detected defective transcriptional output from RNA Pol II recycling following PAF1 depletion. Dynamic ChIP-seq confirmed in vivo PAF1 complex cycling through gene bodies with RNA Pol II and recycling back to the transcription start sites, while PAF1 silencing triggered defective RNA Pol II recycling. Prostate tumors exhibited enhanced transcriptional recycling, which was attenuated by antibody-based PAF1 depletion. These findings identify RNA Pol II recycling as a potential target in cancer and demonstrate the assay’s applicability to characterize RNA Pol II recycling in cells and tissues from other disease states.

ORGANISM(S): Homo sapiens

PROVIDER: GSE133655 | GEO | 2021/10/07

REPOSITORIES: GEO

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Establishment of a novel in vitro transcription assay

Project description:RNA Polymerase II (Pol II) transcriptional recycling is an underappreciated mechanism for which the required factors and contributions to overall gene expression levels are poorly understood. We describe an in vitro methodology facilitating unbiased identification of putative RNA Pol II transcriptional recycling factors and quantitative measurement of transcriptional output from recycled transcriptional components. By combing our in vitro transcription assays with other experiments (e.g. in vivo dynamic ChIP-seq assays), we identified PAF1 complex components as drivers for transcription recycling, revealing a new layer in controlling Pol II-dependent transcription. Our findings also point to RNA Pol II transcription recycling as a mechanism that functions aberrantly in disease states such as cancer, and indicate the potential to target factors such as PAF1 that drive RNA Pol II recycling in cancer.

2021-11-03 | PXD027143 | Pride

Establishment of a novel in vitro transcription assay

Project description:RNA Polymerase II (Pol II) transcriptional recycling is an underappreciated mechanism for which the required factors and contributions to overall gene expression levels are poorly understood. We describe an in vitro methodology facilitating unbiased identification of putative RNA Pol II transcriptional recycling factors and quantitative measurement of transcriptional output from recycled transcriptional components. By combing our in vitro transcription assays with other experiments (e.g. in vivo dynamic ChIP-seq assays), we identified PAF1 complex components and phospho-MED1 as drivers for transcription recycling, revealing a new layer in controlling Pol II-dependent transcription. Our findings also point to RNA Pol II transcription recycling as a mechanism that functions aberrantly in disease states such as cancer, and indicate the potential to target factors such as PAF1 and phospho-MED1 that drive RNA Pol II recycling in cancer.

2021-11-03 | PXD017881 | Pride

Phosphorylated MED1 Links Transcription Recycling and Cancer Growth

Project description:Mammalian RNA polymerase II (Pol II) initiation, elongation, termination and reinitiation are well studied, but how Pol II dynamically recycles after the transcription cycle remains unclear. By establishing in vitro and in vivo transcription recycling systems, we find that human Mediator 1 (MED1), when phosphorylated at the mammal-specific threonine 1032 by cyclin-dependent kinase 9, dynamically travels with Pol II throughout the transcribed genes to drive Pol II recycling. Mechanistically, MED1 phosphorylation leads to an increase of recycled Pol II via the molecular bridge of MED31, enhancing mRNA output during the transcription recycling process. Importantly, MED1 phosphorylation increases during prostate cancer progression to the lethal phase, and pharmacological inhibition of CDK9 decreases prostate tumor growth through decreasing MED1 phosphorylation and Pol II recycling. Our findings reveal essential mechanisms underlying Pol II recycling and suggest a neglected, yet fundamental Pol II transcription process for therapeutic intervention.

2022-04-20 | GSE127894 | GEO

In Vitro Transcription Recycling Assay Identifies PAF1 as a Driver of RNA Pol II Recycling

Project description:In Vitro Transcription Recycling Assay Identifies PAF1 as a Driver of RNA Pol II Recycling

| PRJNA552087 | ENA

SPT6 functions in transcriptional pause/release via PAF1C recruitment

Project description:In vitro studies identified various factors including P-TEFb, SEC, SPT6, PAF1, DSIF, and NELF functioning at different stages of transcription elongation driven by RNA polymerase II (RNA Pol II). What remains unclear is how these factors cooperatively regulate pause/release and productive elongation in the context of living cells. Using an acute 5 protein-depletion approach, prominent release and a subsequent increase in mature transcripts, whereas long genes fail to yield mature transcripts due to a loss of processivity. Mechanistically, loss of SPT6 results in loss of PAF1 complex (PAF1C) from RNA Pol II, leading to NELF-bound RNA Pol II release into the gene bodies. Furthermore, SPT6 and/or PAF1 depletion impairs heat shock-induced pausing, pointing to a role for SPT6 in regulating RNA Pol II pause/release through the recruitment of PAF1C during the early elongation.

2022-08-09 | PXD033771 | Pride

PAF1 regulation of promoter-proximal pause release via enhancer activation

Project description:Gene expression in metazoans is regulated by RNA Polymerase II (Pol II) promoter-proximal pausing and its release. Previously, we identified that Pol II-associated factor 1 (PAF1) modulates the release of paused Pol II into productive elongation. Here, we find that PAF1 occupies transcriptional enhancers and restrains hyperactivation of a subset of these enhancers. Enhancer activation as the result of Paf1 loss releases Pol II from paused promoters of nearby PAF1 target genes. Knockout of PAF1-regulated enhancers attenuates the release of paused Pol II on PAF1 target genes without major interference in the establishment of pausing at their cognate promoters. Thus, a subset of enhancers can primarily modulate gene expression by controlling the release of paused Pol II in a PAF1-dependent manner.

2017-09-01 | GSE97527 | GEO

RNA Polymerase II-associated factor 1 regulates the release and phosphorylation of paused RNA Polymerase II

Project description:Release of promoter-proximal paused RNA polymerase II (Pol II) during early elongation is a critical step in transcriptional regulation in metazoan cells. Paused Pol II release is thought to require the kinase activity of cyclin-dependent kinase 9 (CDK9) for the phosphorylation of DRB sensitivity-inducing factor, negative elongation factor, and C-terminal domain (CTD) serine-2 of Pol II. We found that Pol II-associated factor 1 (PAF1) is a critical regulator of paused Pol II release, that positive transcription elongation factor b (P-TEFb) directly regulates the initial recruitment of PAF1 complex (PAF1C) to genes, and that the subsequent recruitment of CDK12 is dependent on PAF1C. These findings reveal cooperativity among P-TEFb, PAF1C, and CDK12 in pausing release and Pol II CTD phosphorylation. Comparison of the chromatin occupancy of [1] PAF1, CDC73, LEO1, CTR9, total Pol II, and CTD serine 2-phosphorylated Pol II by ChIP-seq in THP1 cells; [2] PAF1, Pol II, Pol II (ser-5p), CDK12, and CDK9 by ChIP-seq in control and PAF1 knockdown cells; [3] LEO1 and Pol II by ChIP-seq in control and flavopiridol treated THP1 cells.

2015-12-11 | E-GEOD-62171 | biostudies-arrayexpress

PAF1, a molecular regulator of promoter-proximal pausing by RNA Polymerase II

Project description:The control of promoter-proximal pausing and the release of RNA polymerase II (RNA Pol II) is a widely used mechanism for regulating gene expression in metazoans, especially for genes that respond to environmental and developmental cues. Here, we identify Pol II associated Factor 1 (PAF1) as a major regulator of promoter-proximal pausing. Knockdown of PAF1 leads to increased release of paused Pol II into gene bodies at thousands of genes. Genes with the highest levels of paused Pol II exhibit the largest redistribution of Pol II from the promoter-proximal region into the gene body in the absence of PAF1. PAF1 depletion results in increased nascent transcription and increased levels of phosphorylation of Pol II’s c-terminal domain on serine 2 (Ser2P). These changes can be explained by the recruitment of the Ser2P kinase Super Elongation Complex (SEC) effecting increased release of paused Pol II into productive elongation, thus establishing a novel function for PAF1 as a major regulator of pausing in metazoans. ChIP-seq of Pol II of different forms, SEC subunits, PAFc subunits and H2Bub in human cell lines targeted by PAF1 or scramble shRNA. ChIP-seq of total Pol II in HCT116 cells targeted by BRE1A or scramble shRNA. ChIP-seq of total Pol II in S2 cells targeted by Paf1 or LacZ RNAi. Total RNA-seq, nascent RNA-seq and GRO-seq in HCT116 cells targeted by PAF1 or scramble shRNA.

2015-08-13 | E-GEOD-70408 | biostudies-arrayexpress

Paf1C regulates RNA polymerase II progression by modulating elongation rate

Project description:Elongation factor Paf1C regulates several stages of the RNA polymerase II (Pol II) transcription cycle, although it is unclear how it modulates Pol II distribution and progression in mammalian cells. We found that conditional ablation of Paf1 resulted in the accumulation of unphosphorylated and Ser5 phosphorylated Pol II around promoter proximal regions and within the first 20-30 kb of gene bodies, respectively. Paf1 ablation did not impact the recruitment of other key elongation factors, namely, Spt5, Spt6, and the FACT complex, suggesting that Paf1 function may be mechanistically distinguishable from each of these factors. Moreover, loss of Paf1 triggered an increase in TSS-proximal nucleosome occupancy, which could impose a considerable barrier to Pol II elongation past TSS-proximal regions. Remarkably, accumulation of Ser5P in the first 20-30 kb coincided with reductions in histone H2B ubiquitylation within this region. Furthermore, we show that nascent RNA species accumulate within this window, suggesting a mechanism whereby Paf1 loss leads to aberrant, prematurely terminated transcripts and diminution of full-length transcripts. Importantly, we found that loss of Paf1 results in Pol II elongation rate defects with significant rate compression. Our findings suggest that Paf1C is critical for modulating Pol II elongation rates by functioning beyond the pause-release step as an "accelerator" over specific early gene body regions.

2019-06-28 | GSE116169 | GEO

Mechanistic basis for selective Mediator-dependence of cell type-specifying transcription

Project description:The Mediator complex routes signals from DNA-binding transcription factors to RNA polymerase (Pol) II. Despite its pivotal position, mechanistic understanding of Mediator in human cells remains incomplete. Here, we quantified Mediator-controlled Pol II kinetics by coupling rapid subunit degradation with orthogonal experimental readouts. Consistent with a model of condensate-driven transcription initiation, large clusters of hypo-phosphorylated Pol II rapidly disassembled upon Mediator degradation. This was accompanied by a selective and pronounced disruption of cell type-specifying transcriptional circuits, whose constituent genes featured exceptionally high rates of Pol II turnover. Remarkably, transcriptional output of most other genes was largely unaffected by acute Mediator ablation. Maintenance of transcriptional activity at these genes was linked to an unexpected, CDK9-dependent compensatory feedback loop that elevated Pol II pause release rates genome-wide. Collectively, our work positions human Mediator as a globally acting coactivator that selectively safeguards the functionality of cell type-specifying transcriptional networks.

2021-09-08 | PXD017611 | Pride

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