Genome-wide dynamics of Pol II elongation and its interplay with promoter proximal pausing, chromatin, and exons
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ABSTRACT: Production of mRNA depends critically on the rate of RNA polymerase II (Pol II) elongation. To dissect Pol II dynamics in mouse ES cells, we inhibited Pol II transcription at either initiation or promoter-proximal pause escape with Triptolide or Flavopiridol, and tracked Pol II kinetically using GRO-seq. Both inhibitors block transcription of more than 95% of genes, showing that pause escape, like initiation, is a ubiquitous and crucial step within the transcription cycle. Moreover, paused Pol II is relatively stable, as evidenced from half-life measurements at ~3200 genes. Finally, tracking the progression of Pol II after drug treatment establishes Pol II elongation rates at over 1,000 genes. Notably, Pol II accelerates dramatically while transcribing through genes, but slows at exons. Furthermore, intergenic variance in elongation rates is substantial, and is influenced by a positive effect of H3K79me2 and negative effects of exon density and CG content within genes. We isolated replicates of nuclei of untreated mESCs and cells treated for 2, 5, 12.5, 25 and 50 min with 300nM flavopiridol, as well as nuclei treated for 12.5, 25, and 50 min with 500nM triptolide and performed GRO-seq with these.
Project description:We used Global Run-on and Sequencing (GRO-seq) to measure the rate of transcription elongation by RNA polymerase II (Pol II) following gene activation. We observed that Pol II elongation rates can vary as much as 4-fold at different genomic loci and in response to two distinct cellular signaling pathways (i.e., estrogen and TNFM-NM-1). Elongation rates are slowest near the promoter and increase during the first ~15 kb transcribed into the gene body. Gene body elongation rates correlate with the density of Pol II, consequently resulting in systematically higher rates of transcript production at genes with higher Pol II density. By monitoring Pol II dynamics following short inductions, we found that E2 stimulates gene expression by increasing Pol II initiation, whereas TNFM-NM-1 stimulates the release of Pol II from promoter proximal pause sites. Collectively, our results identify previously uncharacterized variation in the rate of Pol II elongation and highlight elongation as an important, variable, and regulated rate limiting step in the transcription cycle. Using GRO-seq over a time course (0, 10, 25, and 40 min) of estrogen signaling in ER-alpha positive MCF-7 human breast cancer cells.
Project description:Inhibition of transcriptional elongation plays an important role in gene regulation in metazoans, including C. elegans, which lacks Negative Elongation Factor homologs. Here we combine genomic and biochemical approaches to dissect a novel role of C. elegans AF10 homolog, ZFP-1, in transcriptional control. We show that ZFP-1 and its interacting partner DOT-1.1 have a global role in negatively modulating the level of Pol II transcription on essential widely expressed genes. Moreover,the ZFP-1/DOT-1.1 complex contributes to progressive Pol II stalling on essential genes during development and to rapid Pol II stalling during stress response. The slowing down of Pol II transcription by ZFP-1/DOT-1.1 is associated with an increase in H3K79 methylation and a decrease in H2B monoubiquitination, which promotes transcription. We propose a model where recruitment of ZFP-1/DOT-1.1 and deposition of H3K79 methylation at highly expressed genes initiates a negative feedback mechanism for modulation of their expression. GRO-seq (Global Run-On sequening) for nascent transcript detectiong on WT and zfp-1(ok554) mutant nematode (C. elegans) larvae in L3 stage, performed in duplicate per condition (4 samples total).
Project description:Inflammation is associated with many cardiovascular pathologies, but the underlying mechanisms remain unclear. To explore this in more detail, we characterized the transcriptome of an immortalized adult human ventricular cardiomyocyte cell line (AC16) in response to tumor necrosis factor (TNFa). Using a combination of genomic approaches, including global nuclear run-on sequencing (GRO-seq) and chromatin immunoprecipitation coupled with sequencing (ChIP-seq), we identified ~30,000 transcribed regions in AC16 cells, which includes a set of RNA polymerases I and III (Pol I and Pol III) transcribed regions revealed in the presence of M-NM-1-amanitin. The set of transcribed regions produces both protein-coding and non-coding RNAs, many of which have not been annotated previously, including enhancer RNAs originating from NF-M-NM-:B binding sites. In addition, we observed that AC16 cells rapidly and dynamically reorganize their transcriptomes in response to TNFa stimulation in an NF-M-NM-:B-dependent manner, switching from a basal state to a proinflammatory state affecting a spectrum of cardiac-associated protein-coding and non-coding genes. Moreover, we observed distinct Pol II dynamics for up- and downregulated genes, with a rapid release of Pol II into productive elongation for TNFa-stimulated genes. Our studies shed new light on the regulation of the cardiomyocyte transcriptome in response to a proinflammatory signal and help to clarify the link between inflammation and cardiomyocyte function at the transcriptional level. Using GRO-seq and ChIP-seq (p65 and RNA Pol II) over a time course of TNFM-NM-1 signaling in AC16 human cardiomyocytes.
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:Argonaute proteins and their small RNA co-factors short interfering RNAs (siRNAs) are known to inhibit gene expression at the transcriptional and post-transcriptional levels. In Caenorhabditis elegans, the Argonaute CSR-1 binds thousands of endogenous siRNAs (endo-siRNAs) antisense to germline transcripts and associates with chromatin in a siRNA-dependent manner. However, its role in gene expression regulation remains controversial. Here, we used a genome-wide profiling of nascent RNA transcripts to demonstrate that the CSR-1 RNAi pathway promotes sense-oriented Pol II transcription. Moreover, a loss of CSR-1 function resulted in global increase in antisense transcription and ectopic transcription of silent chromatin domains, which led to reduced chromatin incorporation of centromere-specific histone H3. Based on these findings, we propose that the CSR-1 pathway has a role in maintaining the directionality of active transcription thereby propagating the distinction between transcriptionally active and silent genomic regions. GRO-seq (Global Run-On sequencing) for detection of nascent transcripts. Two biological replicates were generated for csr-1 hypomorphic mutant and the corresponding WT samples using ~300,000 worms for each experiment, and two biological replicates were prepared for drh-3 (ne4253) mutant and the corresponding WT samples using ~100,000 worms for each experiment. The GRO-seq were performed in late L3/early L4 stage worms. (8 samples total)
Project description:Densely sampled time course GRO-seq analysis was performed to determine global transcriptional activities at both enhancers and promoters upon Sendai Virus infection.
Project description:RNA polymerase II is decreased on heat shock-induced genes when the CTD phosphatase Fcp1 is knocked down in Drosophila S2 cells. We examined transcriptionally-engaged Pol II genome-wide with GRO-seq to determine if other genes are similarly affected. Two biological replicates of nascent RNA sequencing
Project description:Distal enhancers characterized by H3K4me1 mark play critical roles in developmental and transcriptional programs. However, potential roles of specific distal regulatory elements in regulating RNA Polymerase II (Pol II) promoter-proximal pause release remain poorly investigated. Here we report that a unique cohort of jumonji C domain-containing protein 6 (JMJD6) and bromodomain-containing protein 4 (Brd4) co-bound distal enhancers, termed anti-pause enhancers (A-PEs), regulate promoter-proximal pause release of a large subset of transcription units via long-range interactions. Brd4-dependent JMJD6 recruitment on A-PEs mediates erasure of H4R3me2(s), which is directly read by 7SK snRNA, and decapping/demethylation of 7SK snRNA, ensuring the dismissal of the 7SKsnRNA/HEXIM inhibitory complex. The interactions of both JMJD6 and Brd4 with the P-TEFb complex permit its activation and pause release of regulated coding genes. The functions of JMJD6/ Brd4-associated dual histone and RNA demethylase activity on anti-pause enhancers have intriguing implications for these proteins in development, homeostasis and disease. All Gro-seq(s) were designed to reveal the transcriptional targets of JMJD6 and Brd4, and assess the role of JMJD6 and Brd4 in Pol II promoter-proximal pause release. All ChIP-seq(s) were designed to understand the unique features, associated molecular mechanisms and functions of the anti-pause enhancers (A-PEs) discovered in the current study.
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.
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.