Project description:Protein phosphatase 1 complex (PP1C), consisting of one of the phosphatases, PP1α, β and γ, and three regulatory subunits PNUTS, TOX4 and WDR82, plays critical roles in gene regulation and is mutated in over 20% uterine corpus endometrial carcinoma cases. Here we show that knockdown of PP1γ reduced chromatin occupancy of RNA polymerase II (Pol II), but increased the cellular level and chromatin occupancy of Ser-2 phosphorylated Pol II and Ser-5 phosphorylated Pol II. 4sUDRB-seq data showed that the Pol II elongation rate decreased upon PP1γ loss. These results advanced our understanding of the roles of PP1γ in transcriptional regulation.
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.
Project description:The Pol II elongation rate influences poly(A) site selection, with slow and fast Pol II derivatives causing upstream and downstream shifts, respectively, in poly(A) site utilization. In yeast, depletion of either of the histone chaperones FACT or Spt6 causes an upstream shift of poly(A) site use that strongly resembles the poly(A) profiles of slow Pol II mutant strains. Like slow Pol II mutant strains, Spt6- and FACT-depleted cells exhibit processivity defects, indicating that both Spt6 and FACT stimulate the Pol II elongation rate. Poly(A) profiles of some genes show atypical downstream shifts; this subset of genes overlaps well for FACT- or Spt6- depleted strains, but it is different from the atypical genes in Pol II speed mutant strains. In contrast, depletion of histone H3 or H4 causes a downstream shift of poly(A) sites for most genes, indicating that nucleosomes inhibit the Pol II elongation rate in vivo. Thus, chromatin-based control of the Pol II elongation rate is a potential mechanism, distinct from direct effects on the cleavage/polyadenylation machinery, to regulate alternative polyadenylation in response to genetic or environmental changes.
Project description:We performed PRO-Seq to measure the Pol II elongation rate by measruing the distance of Pol II travels at viarous time points after relased from DRB induced pausing. We compared DMSO/DRB or THZ531/DRB co-treated sample to assess the effect of CDK12 and CDK13 inhibtion by THZ531 on transcriptional elongation rate.
Project description:Recent studies reveal a striking phenomenon that RNA Polymerase II (Pol II) appears to travel on gene body in an accelerated fashion, but the mechanism has remained unknown. We performed synchronized transcription coupled with deep sequencing, observing an inverse relationship between initial rate and acceleration in different cell types. We directly tested several correlative events and detected a positive contribution of the splicing commitment factor SRSF2 to Pol II acceleration, suggesting a functional benefit of co-transcriptional pre-mRNA splicing in transcription elongation. Unexpectedly, we found that perturbation of Pol II Ser2 phosphorylation had little impact on Pol II elongation or acceleration. While H3K79me2 has been positively correlated with Pol II elongation, we showed that reduction of this histone modification event actually accelerated Pol II elongation. Together, these data suggest a combined effect of gradual gain-of-competence and gradual lost-of-epigenetic barriers as the mechanism for accelerated Pol II elongation. DRB time-course releasing assay under functional perturbation
Project description:To study the impact of the RNA polymerase II (Pol II) elongation rate on gene expression, we used CRISPR-Cas9 genome editing in S. pombe to generate a "slow" Pol II mutant with decreased elongation rate. Although the mutation is well tolerated as far as cell growth is concerned, transcriptomic analyses revealed that the slow mutant tends to terminate transcription prematurely. We distinguished two mechanisms by which premature termination affects gene expression in the slow mutant: It either (1) shortens 3'UTR, or (2) derepresses protein coding genes by prematurely terminating upstream interfering RNAs. Strikingly, the genes affected by these mechanisms are enriched for genes involved in phosphate uptake and purine synthesis, two processes essential for the maintenance of the nucleotide pool of the cell. Together with evidences that nucleotides are conditional for Pol II processive elongation, our results suggest that Pol II elongation rate acts as both sensor and effector in response to nucleotide depletion.
Project description:The objective of this study was to investigate the relationship between Pol I transcription elongation rate and ribosomal RNA processing in vivo by using a yeast strain containing a mutation in Pol I. This mutation, rpa190-F1205H, has been previously characterized to have a reduced elongation rate in vitro. Here, we used native elongating transcript sequencing (NET-seq) to determine the effect of this mutation on Pol I occupancy in vivo. Our findings demonstrate that this mutation induces increased Pol I pausing, especially in the first half of the 35S gene, and causes sequence-specific changes in Pol I occupancy.
Project description:Yeast mRNAs are polyadenylated at multiple sites in their 3’ untranslated regions (3’UTRs), and poly(A) site usage is regulated by the rate of transcriptional elongation by RNA polymerase II (Pol II). Slow Pol II derivatives favor upstream poly(A) sites and fast Pol II derivatives favor downstream poly(A) sites. Transcriptional elongation and polyadenylation are linked at the nucleotide level, presumably reflecting Pol II dwell time at each residue that influences the level of polyadenylation. Here, we investigate the relationship between Pol II pause sites and poly(A) sites within 3’UTRs.
Project description:The rate of RNA polymerase II (pol II) elongation can influence splice site selection in nascent transcripts, yet the extent and physiological relevance of this kinetic coupling between transcription and alternative splicing is not well understood. We performed experiments to perturb pol II elongation and then globally compared alternative splicing patterns with genome-wide pol II occupancy. RNA binding and RNA processing functions were significantly enriched among the genes with pol II elongation inhibition-dependent changes in alternative splicing. Under conditions that interfere with pol II elongation, including cell stress, increased pol II occupancy was detected in the intronic regions flanking the alternative exons in these genes, and these exons generally became more included. A disproportionately high fraction of these exons introduced premature termination codons that elicited nonsense-mediated mRNA decay (NMD), thereby further reducing transcript levels. Our results provide evidence that kinetic coupling between transcription, alternative splicing and NMD affords a rapid mechanism by which cells can respond to changes in growth conditions, including cell stress, to coordinate the levels of RNA processing factors with mRNA levels. In order to identify alternative splicing events influenced by changes in pol II elongation, we performed quantitative alternative splicing microarray profiling (Pan et al., 2004 (PMID 15610736); Shai et al., 2006 (PMID 16403798)) of RNA isolated from stimulated Jurkat T lymphoma cells, cultured separately in the presence or absence of two different drugs that can inhibit pol II elongation: 5,6-dichloro-1-β-D-ribofuranosyl-benzimidazole (DRB) and camptothecin.