Knockdown of Brd4 or SEC affects the HMBA-induced global Pol II pausing release
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ABSTRACT: To test whether Brd4 and SEC co-regulate the release of promoter-proximally paused Pol II, we performed Pol II ChIP-Seq to analyze the effect of depletion of Brd4 or SEC on HMBA-induced pause release in HCT116 cells.
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.
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.
Project description:Metazoan gene expression is often regulated after the recruitment of RNA polymerase II (Pol II) to promoters, through the controlled release of promoter-proximally paused Pol II into productive RNA synthesis. Despite the prevalence of paused Pol II, very little is known about the dynamics of these early elongation complexes or the fate of short transcription start site-associated (tss) RNAs they produce. Here, we demonstrate that paused elongation complexes can be remarkably stable, with half-lives exceeding 15 minutes at genes with inefficient pause release. Promoter-proximal termination by Pol II is infrequent and released tssRNAs are targeted for rapid degradation. Further, we provide evidence that the predominant tssRNA species observed are nascent RNAs held within early elongation complexes. We propose that stable pausing of polymerase provides a temporal window of opportunity for recruitment of factors to modulate gene expression and that the nascent tssRNA represents an appealing target for these interactions. This submission includes 13 raw data files. Four samples (chromatin, soluble, mock-treated, and Rrp40-depleted) are represented by two biological replicate raw data files, while five samples (cells, DMSO, FP, mock-treated + FP, and Rrp-40depleted + FP) are represented by single raw data files.
Project description:Metazoan gene expression is often regulated after the recruitment of RNA polymerase II (Pol II) to promoters, through the controlled release of promoter-proximally paused Pol II into productive RNA synthesis. Despite the prevalence of paused Pol II, very little is known about the dynamics of these early elongation complexes or the fate of short transcription start site-associated (tss) RNAs they produce. Here, we demonstrate that paused elongation complexes can be remarkably stable, with half-lives exceeding 15 minutes at genes with inefficient pause release. Promoter-proximal termination by Pol II is infrequent and released tssRNAs are targeted for rapid degradation. Further, we provide evidence that the predominant tssRNA species observed are nascent RNAs held within early elongation complexes. We propose that stable pausing of polymerase provides a temporal window of opportunity for recruitment of factors to modulate gene expression and that the nascent tssRNA represents an appealing target for these interactions.
Project description:Transcriptional regulation of developmentally controlled genes is at the heart of differentiation and organogenesis. In this study, we have performed global genomic analyses in murine embryonic stem (ES) cells and in human cells in response to activation signals. We have identified an essential role for the ELL/P-TEFbcontaining Super Elongation Complex (SEC) in the regulation of gene expression including several genes bearing paused RNA polymerase II (Pol II). Paused Pol II has been proposed to be associated with loci that respond rapidly to environmental stimuli. However, our studies in ES cells have also identified a requirement for SEC at genes without preloaded Pol II, which also respond dynamically to differentiation signals. Our findings suggest that SEC is a major class of active P-TEFb-containing complexes required for transcriptional activation in response to environmental cues such as differentiation signals. Examination of ELL2, AFF4, and Pol II before and after activation signals in two cell types.
Project description:Transcriptional regulation of developmentally controlled genes is at the heart of differentiation and organogenesis. In this study, we have performed global genomic analyses in murine embryonic stem (ES) cells and in human cells in response to activation signals. We have identified an essential role for the ELL/P-TEFbcontaining Super Elongation Complex (SEC) in the regulation of gene expression including several genes bearing paused RNA polymerase II (Pol II). Paused Pol II has been proposed to be associated with loci that respond rapidly to environmental stimuli. However, our studies in ES cells have also identified a requirement for SEC at genes without preloaded Pol II, which also respond dynamically to differentiation signals. Our findings suggest that SEC is a major class of active P-TEFb-containing complexes required for transcriptional activation in response to environmental cues such as differentiation signals.
Project description:The super elongation complex (SEC) is required for robust and productive transcription through release of RNA polymerase II (Pol II) with its P-TEFb module and promoting transcriptional processivity with its ELL2 subunit. Malfunction of SEC contributes to multiple human diseases including cancer. Here, we identify peptidomimetic lead compounds, KL-1 and its structural homolog KL-2, which disrupt the interaction between the SEC scaffolding protein AFF4 and P-TEFb, resulting in impaired release of Pol II from promoter-proximal pause sites and a reduced average rate of processive transcription elongation. SEC is required for induction of heat-shock genes and treating cells with KL-1 and KL-2 attenuates the heat-shock response from Drosophila to human. SEC inhibition downregulates MYC and MYC-dependent transcriptional programs in mammalian cells and delays tumor progression in a mouse xenograft model of MYC-driven cancer, indicating that small-molecule disruptors of SEC could be used for targeted therapy of MYC-induced cancer.
Project description:The transition from transcription initiation to elongation is a key regulatory step in gene expression, which requires RNA polymerase II (Pol II) to escape promoter proximal pausing on chromatin. While elongation factors promote pause release leading to transcription elongation, the role of epigenetic modifications during this critical transition step is poorly understood. Two histone marks on histone H3, lysine 4 trimethylation (H3K4me3) and lysine 9 acetylation (H3K9ac), co-localize on active gene promoters and are associated with active transcription. H3K4me3 can promote transcription initiation, yet the functional role of H3K9ac is much less understood. We hypothesized that H3K9ac may function downstream of transcription initiation by recruiting specific proteins important for the next step of transcription. Here, we describe a functional role for H3K9ac in promoting Pol II pause release by directly recruiting the super elongation complex (SEC) to chromatin. H3K9ac serves as a substrate for direct binding of the SEC, as does acetylation of histone H4 lysine 5 (H4K5ac), to a lesser extent. Furthermore, lysine 9 on histone H3 is necessary for maximal Pol II pause release through SEC action, and loss of H3K9ac increases the Pol II pausing index on a subset of genes in HeLa cells. At select gene promoters, loss of H3K9ac or depletion of the SEC reduces gene expression and increases paused Pol II occupancy. We therefore propose that an ordered histone code drives progression through the transcription cycle, providing new mechanistic insight that SEC recruitment to certain acetylated histones promotes the subsequent release of paused Pol II needed for transcription elongation.
Project description:The transcriptional progression is regulated by SPT5, which is involved in both promoter-proximal RNA polymerase II (Pol II) pausing and elongation, which serve as rate-limiting steps in metazoan. However, the mechanism for SPT5 coordinating these processes remains unclear. Here we report that the disordered sub-regions within SPT5 contain a prion-like domain (PLD) that is required for Pol II pausing, while the phosphorylation site-rich domain (PRD) is essential for transcript elongation. Mechanically, SPT5-PLD helps stabilize Pol II pausing by preventing SPT5-PRD phosphorylation mediated by the super elongation complex (SEC). SPT5-PLD also maintains Pol II pausing by recruiting a newly identified transcriptional pause regulator, PSIP1, which inhibits phosphorylation required for elongation. Additionally, SPT5-PLD prevents premature release of Pol II pausing through PSIP1’s IBD domain by counteracting SEC. Our results demonstrate that SPT5 possesses intrinsic characteristics that balance the transcriptional process by preventing premature pause release and promoting progression to elongation.