Pre-mRNA Splicing is Facilitated by an Optimal RNA Polymerase II Elongation Rate
ABSTRACT: Transcription and pre-mRNA alternative splicing was analyzed by in isogenic human HEK293 cell lines that inducibly express a-amanitin resistant mutants of the RNA polymerase II large subunit with slow and fast elongation rates. Alternative splicing was analyzed by, RNA-seq and RASL-seq of polyA+ RNA from a-amanitin treated cells; transcription elongation rate was analyzed by BrUTP-labelled GRO-seq of a-amanitin treated cells at time points after release from a DRB (5,6-dichloro-1-bold beta-D-ribofuranosylbenzimidazole) block.
Project description:Transcription termination was analyzed by anti RNA pol II ChIP-seq in isogenic human HEK293 cell lines that inducibly express a-amanitin resistant mutants of the RNA polymerase II large subunit with slow and fast elongation rates and in lines that inducbily over-express WT or an active site mutant of the RNA exonuclease "torpedo" Xrn2. Transcription termination zones were mapped by anti-pol II ChIP-seq under conditions where transcription elongation rate was increased or decreased by point mutations in the large subunit of the enzyme. Termination was also assayed under conditions where Xrn2 exonuclease activity was inhibited by over-expression of an active site mutant (D235A).
Project description:RBM10 is an RNA binding protein that was identified as a component of spliceosome complex, suggesting its potential role in splicing regulation. However, the direct experimental evidence for this function has been lacking. Here we characterized in vivo RBM10-RNA interactions and investigated the role of RBM10 in splicing regulation at the global level. We observed significant RBM10-RNA interactions in the vicinity of splice sites and identified hundreds of splicing changes following perturbation of cellular RBM10 abundance. A RNA splicing map integrating the binding pattern and splicing profiles revealed a significant correlation between RBM10-enhanced exon skipping events and its binding close to the splicing sites of both upstream and downstream introns. Furthermore, we demonstrated the splicing defects in a patient carrying a RBM10 mutation. Overall, our data provided insights into the mechanistic model of RBM10-mediated splicing regulation and established genomic resources for future studies on its function in different pathophysiological contexts. We sequenced the mRNA of HEK293 cells and LCL cells, and we determined the RBM10 binding sites using PARCLIP in HEK293 cells. In total we sequenced four mRNA-Seq libraries for KD and two for OE in HEK293 cells; for each of these libraries, we also sequenced one control library. We also sequenced the mRNA of one patient LCL and two normal LCL libraries. Two replicates of PARCLIP sequencing were perfomed.
Project description:RNAP II is frequently paused near gene promoters in mammals and its transition to productive elongation requires active recruitment of P-TEFb, a cyclin-dependent kinase for RNAP II and other key transcription elongation factors. A fraction of P-TEFb is sequestered in an inhibitory complex containing the 7SK noncoding RNA, but it has been unclear how P-TEFb is switched from the 7SK complex to RNAP II during transcription activation. We report that SRSF2 (also known as SC35, an SR splicing factor) is part of the 7SK complex assembled at gene promoters and plays a direct role in transcription pause release. We demonstrate RNA-dependent, coordinated release of SRSF2 and P-TEFb from the 7SK complex and transcription activation via SRSF2 binding to promoter-associated nascent RNA. These findings reveal an unanticipated SR protein function, a role for promoter-proximal nascent RNA in gene activation, and an analogous mechanism to HIV Tat/TAR for activating cellular genes. SR ChIP-seq, Pol II ChIP-seq, and Gro-seq
Project description:The Carboxy-terminal domain (CTD) of RNA Polymerase II (RNAPII) in mammals undergoes extensive post-translational modification, which is essential for transcriptional initiation and elongation. Here, we show that the CTD of RNAPII is methylated at a single arginine (R1810) by the transcriptional co-activator CARM1. Although methylation at R1810 is present on the hyper-phosphorylated form of RNAPII in vivo, Ser-2 or Ser-5 phosphorylation inhibit CARM1 activity towards this site in vitro, suggesting that methylation occurs before transcription initiation. Mutation of R1810 results in the mis-expression of a variety of snRNAs and snoRNAs, an effect that is also observed in Carm1-/- MEFs. These results demonstrate that CTD methylation facilitates the expression of select RNAs, perhaps serving to discriminate the RNAPII-associated machinery recruited to distinct gene types. To address the function of RNAPII methylation, we generated Raji cell lines expressing an RNA Polymerase II resistant to α-amanitin and carrying either wild-type R1810 or an arginine to alanine substitution at that same residue, abolishing R1810 methylation of the CTD. In cells cultured in α-amanitin, the α-amanitin-resistant mutants fully replaced the functions of endogenous RNAPII, allowing us to study if gene-expression is affected by the absence of R1810me
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. To monitor pol II distributions, chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-Seq) was performed using an anti-pol II antibody (4H8) and cross-linked chromatin preparations from Jurkat cells, treated with or without pol II elongation inhibitor 5,6-dichloro-1-β-D-ribofuranosyl-benzimidazole (DRB) at 10 and 25 ug/ml respectively prior to phorbol 12-myristate 13-acetate (PMA) stimulation, for 5000+ alternative splicing events.
Project description:During development histone modifying enzymes are required for cell identity and lineage commitment, however little is known about the regulatory origins of the epigenome during embryonic development. Here we generate a comprehensive set of embryonic epigenome reference maps, which we use to determine the extent to which maternal factors shape chromatin state in Xenopus embryos. Using α-amanitin to inhibit zygotic transcription, we find that the majority of H3K4me3 and H3K27me3-enriched regions form a maternally defined epigenetic regulatory space with an underlying logic of hypomethylated islands. This maternal regulatory space extends to a substantial proportion of neurula stage-activated promoters. In contrast, p300-recruitment to distal regulatory regions requires embryonic transcription at most loci. The results show that H3K4me3 and H3K27me3 are part of a regulatory space that exerts an extended maternal control well into post-gastrulation development, and highlight the combinatorial action of maternal and zygotic factors through proximal and distal regulatory sequences. We have performed ChIP-sequencing of eight histone modifications, RNA polymerase II (RNAPII) and the enhancer protein p300 at five stages of development: blastula (st. 9), gastrula (st. 10.5, 12.5), neurula (st. 16) and tailbud (st. 30). These experiments allow identification of enhancers (H3K4me1, p300), promoters (H3K4me3, H3K9ac), transcribed regions (H3K36me3, RNAPII) and repressed and heterochromatic domains (H3K27me3, H3K9me2, H3K9me3, H4K20me3). In addition we generated pre-MBT (st. 8) maps for three histone modifications (H3K4me3, H3K9ac, H3K27me3) and single-base resolution DNA methylome maps using whole genome bisulfite sequencing of blastula and gastrula (st. 9 and 10.5) embryos. To determine the maternal and zygotic contributions to chromatin state, we used alpha-amanitin to block embryonic transcription. Fertilised eggs were injected with 2.3 nl of 2.67 ng/ul alpha-amanitin and developed until the control embryos reached mid-gastrulation. Alpha-amanitin and control embryos were used for RNA-seq and ChIP-seq of RNAPII, H3K4me3, H3K27me3 and p300. For all ChIP-seq samples of the epigenome reference maps and RNAPII ChIP-seq samples of the α-amanitin experiments three biological replicates of different chromatin isolations of 45 embryos were pooled. Two biological replicates for H3K4me3 (α-amanitin injected: resp. 90 and 56 embryo equivalents (eeq); control: resp. 45 and 67 eeq), H3K27me3 (α-amanitin injected: resp. 90 and 180 eeq; control: resp. 45 and 202 eeq) and p300 (α-amanitin injected: resp. 112 and 56 eeq; control: resp. 112 and 67 eeq) ChIP-seq samples of the α-amanitin experiments were generated. For RNA-seq samples of the α-amanitin experiments RNA from 5 embryos from one biological replicate was isolated and depleted of ribosomal RNA
Project description:Transcription and pre-mRNA alternative splicing was analyzed by in isogenic human HEK293 cell lines that inducibly express a-amanitin resistant mutants of the RNA polymerase II large subunit with slow and fast elongation rates. Overall design: Alternative splicing was analyzed by, RNA-seq and RASL-seq of polyA+ RNA from a-amanitin treated cells; transcription elongation rate was analyzed by BrUTP-labelled GRO-seq of a-amanitin treated cells at time points after release from a DRB (5,6-dichloro-1-bold beta-D-ribofuranosylbenzimidazole) block.
Project description:HEK293T cells were transfected with the Rbp1-amr or slow (R729H-amr) α-amanitin resistant subunit of RNA Pol II and selected with α-amanitin 24 hours after transfection for additional 24 hours. Total RNA was extracted and global changes in gene expression were determined using microarray chips. MiRNAs are transcribed by RNA pol II but the transcriptional features influencing their synthesis are poorly defined. Here we report that a TATA-box in miRNA and a subset of protein-coding genes is associated with increased sensitivity to a slow rate of transcription elongation. We also show that promoters driven by TATA-box or NF-κB elicit high transcription re-initiation rate, but paradoxically lower levels of miRNA. Interestingly, miRNA synthesis was converted to a more productive mode by decreasing initiation rate, but less productive when the re-initiation rate increased. This phenomenon was found to be associated with a delay in miR-146a induction by NF-κB. We also demonstrate that miRNAs are remarkably strong pause sites. Our findings suggest that lower efficiency of miRNA synthesis directed by the TATA-box or NF-κB is a consequence of frequent transcription initiation that lead to Pol II crowding at pause sites, thereby increasing the chance of collision and premature termination. These findings highlight the importance of the transcription initiation mechanism for miRNA synthesis, and have implications for TATA-box promoters in general. HEK293T cells were transfected with plasmids directing the expression of α-amanitin-resistant variants of Pol II (Rpb1-amr and R749H-amr). α-amanitin was added and RNA was prepared 24 and 48 h later, respectively. The data provided is from 3 Rpb1-amr vs 3 R749H-amr (6 samples).
Project description:This SuperSeries is composed of the following subset Series: GSE25287: Global impact of RNA polymerase II elongation inhibition on alternative splicing regulation (expression) GSE25494: Global impact of RNA polymerase II elongation inhibition on alternative splicing regulation (ChIP-Seq) Refer to individual Series
Project description:Xenopus laevis embryos were injected with alpha-amanitin to inhibit RNA polymerase II activity. Embryos were allowed to develop up to stage 10.5 (early gastrula, control and alpha-amanitin injected embryos) and subsequently collected for RNA isolation. The transcriptome profiles of alpha-amanitin injected and control embryos were compared.