Mammalian NET-seq reveals genome-wide nascent transcription coupled to RNA processing
ABSTRACT: We have generated single-nucleotide resolution, nascent transcription profiles from HeLa cells by developing Native Elongation Transcript sequencing technology for mammalian chromatin (mNET-seq). Our extensive data sets provide a substantial resource to study mammalian nascent transcript profiles. We reveal unanticipated phosphorylation states for RNA polymerase II C-terminal domain (Pol II CTD) at both gene ends. We also observe that following 5’ splice site cleavage by the spliceosome, upstream exon transcripts are tethered to Pol II CTD phosphorylated on the serine 5 position (S5P) which is accumulated over downstream exons. We further show that depletion of termination factors substantially reduces Pol II pausing at gene ends leading to termination defects. Remarkably termination factors play an additional promoter role by restricting non-productive RNA synthesis and redistributing Pol II CTD S2P to promoters. These data demonstrate that CTD phosphorylation is more dynamic and variably distributed across mammalian transcription units than previously envisaged. To monitor nascent RNA within the mammalian Pol II complex, and its association with different CTD phosphorylation states, we employed mNET-seq methodology on HeLa cells, complemented with direct sequencing of chromatin-bound RNA (ChrRNA-seq). mNET-seq was preformed using the antibodies 8WG16, CMA602, CMA603 and CMA601, which are specific for unphosphorylated CTD, Ser2 phosphorylation, Ser5 phosphorylation and all CTD isoforms, respectively. In another experiment, to evaluate the effect of transcription termination factors in nascent RNA production by Pol II, mNET-seq and complemented with ChrRNA-seq was preformed on HeLa cells transfected with siRNA against PTBP1, CPSF73, CstF64+CstF64tau or Xrn2, and the gene profiles were compared with profiles from HeLa transfected with siRNA for Luciferase generated by the same protocol.
Project description:Transcription controls splicing and other gene regulatory processes, yet mechanisms remain obscure due to our fragmented knowledge of the molecular connections between the dynamically phosphorylated RNA polymerase II (Pol II) C-terminal domain (CTD) and regulatory factors. By systematically isolating phosphorylation states of the CTD heptapeptide repeat (Y1S2P3T4S5P6S7), we identify hundreds of protein factors that are differentially enriched, revealing unappreciated connections between the Pol II CTD and co-transcriptional processes. These data uncover a novel role for threonine-4 in 3’ end processing through controlling the transition between cleavage and termination. Furthermore, serine-5 phosphorylation seeds spliceosomal assembly immediately downstream of 3’ splice sites through a direct interaction with spliceosomal subcomplex, U1. Strikingly, threonine-4 phosphorylation also impacts splicing through serving as a mark of spliceosomal release and ensuring efficient post-transcriptional splicing genome-wide. Thus, comprehensive Pol II interactomes identify the complex and functional connections between transcription machinery and other gene regulatory complexes. Overall design: NET-seq of WT, rai1, rtt103 and Pol II CTD threonine-4 mutants. Nascent RNA-seq of WT and Pol II CTD threonine-4 mutant. RNA-seq of WT and Pol II CTD threonine-4 mutants. ChIP-nexus analysis of phospho-Ser5 and phospho-Thr4 of the Pol II CTD and ChIP-nexus of splicing factors.
Project description:ChIP-chip was performed to identify the genomic binding locations for the termination factors Nrd1, and Rtt103, and for RNA polymerase (Pol) II phosphorylated at the tyrosine 1 and threonine 4 position of its C-terminal domain (CTD). In different phases of the transcription cycle, Pol II recruits different factors via its CTD, which consists of heptapeptide repeats with the sequence Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7. Here we show that the CTD of transcribing yeast Pol II is phosphorylated at Tyr1, and that this impairs recruitment of termination factors. Tyr1 phosphorylation levels rise downstream of the transcription start site (TSS), and decrease before the polyadenylation (pA) site. Tyr1-phosphorylated gene bodies are depleted of CTD-binding termination factors Nrd1, Pcf11, and Rtt103. Tyr1 phosphorylation blocks CTD binding by these termination factors, but stimulates binding of elongation factor Spt6. These results show that CTD modifications can not only stimulate but also block factor recruitment, and lead to an extended CTD code for transcription cycle coordination.
Project description:At the 3'-ends of genes, RNA polymerase (Pol) II is dephosphorylated at tyrosine 1 residues of its C-terminal domain (CTD), resulting in recruitment of transcription termination factors. We show that the multisubunit cleavage and polyadenylation factor (CPF) is a Pol II CTD phosphatase and its Glc7 subunit is required for Tyr1 dephosphorylation at the poly-adenylation site and Pol II termination in vivo. ChIP-chip was performed to examine the effect of Glc7 nuclear depletion on genome-wide Pol II occupancy [using ?-Rpb3 (1Y26, cat. no. W0012, neoclone) antibody] and CTD tyrosine 1 phosphorylation levels [using ?-TyrY1P (3D12, D. Eick) antibody].
Project description:In Saccharomyces cerevisiae short non-coding RNA (ncRNA) generated by RNA Polymerase II (Pol II) are terminated by the NRD complex consisting of Nrd1, Nab3 and Sen1. We now show that Pcf11, a component of the cleavage and polyadenylation complex (CPAC), is generally required for NRD-dependent transcription termination through the action of its CTD interacting domain (CID). Pcf11 localizes downstream of Nrd1 on NRD terminators, and its recruitment depends on Nrd1. Furthermore mutation of the Pcf11 CID results in Nrd1 retention on chromatin, delayed degradation of ncRNA and restricts Pol II CTD Ser2 phosphorylation and Sen1-Pol II interaction. Finally, the pcf11-13 and sen1-1 mutant phenotypes are very similar as both accumulate RNA:DNA hybrids and display Pol II pausing downstream of NRD terminators. We predict a mechanism whereby Nrd1 and Pcf11 exchange on chromatin facilitates Pol II pausing and CTD Ser2-P phosphorylation. This in turn promotes Sen1 activity that is required for NRD-dependent transcription termination in vivo. ChIP-seq with antibody against pol II in wild type and Pcf11 mutants: Pcf11-2, Pcf11-9 and Pcf11-13 grown at 25C and 37C along with input samples
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  PAF1, CDC73, LEO1, CTR9, total Pol II, and CTD serine 2-phosphorylated Pol II by ChIP-seq in THP1 cells;  PAF1, Pol II, Pol II (ser-5p), CDK12, and CDK9 by ChIP-seq in control and PAF1 knockdown cells;  LEO1 and Pol II by ChIP-seq in control and flavopiridol treated THP1 cells.
Project description:Numerous long intervening non-coding RNA (lincRNA) are generated from the mammalian genome by RNA polymerase II (Pol II) transcription. Although multiple functions have been ascribed to lincRNA, their synthesis and turnover remain poorly characterised. Here we define systematic differences in transcription and RNA processing between protein-coding and lincRNA genes in human HeLa cells. This is based on a range of nascent transcriptomic approaches applied to different nuclear fractions, including mammalian native elongating transcript sequencing (mNET-seq). Notably mNET-seq patterns specific for different Pol II CTD phosphorylation states reveal weak co-transcriptional splicing and poly(A) signal independent Pol II termination on lincRNA as compared to pre-mRNA. In addition, lincRNA are mostly restricted to chromatin where they are co-transcriptionally degraded by the RNA exosome. We also show that a lincRNA specific co-transcriptional RNA cleavage mechanism acts to induce premature termination. In effect functional lincRNA must escape from this targeted nuclear surveillance process. Overall design: We employed CTD phospho specific mNET-Seq with pla-B splicing inhibitor and RNA processing factors knockdown (DGCR8, Dicer1, EXOSC3 and CPSF73 proteins). mNET-seq experiments with 1% Empigen detergent treatment were performed to separate Pol II-associated complex from Pol II. We also analyzed subcellur RNA and pA+ and pA- nucleoplasm RNA libraries for RNA processing efficiency and the turnover. There are 4 raw files come from an illumina experiment (per sample), produced in 2 lanes. They were all mapped together.
Project description:Using pol II mutants in human cells we found that slow transcription repositioned specific co-transcriptionally deposited chromatin modifications; H3K36me3 shifted within genes toward 5’ ends and H3K4me2 extended further upstream of start sites. Slow transcription also evoked a hyperphosphorylation of CTD Ser2 residues at 5’ ends of genes that is conserved in yeast. We propose a “dwell-time in the target zone” model to explain the effects of transcriptional dynamics on establishment of co-transcriptionally deposited protein modifications. Promoter-proximal Ser2 phosphorylation is associated with longer pol II dwell time at start sites and reduced transcriptional polarity due to strongly enhanced divergent antisense transcription at promoters. Overall design: The effect of transcription elongation rate on histone H3K36me3, H3K4me2 and pol II CTD phosphorylation was analyzed by ChIP-seq in isogenic human HEK293 cell lines that inducibly express a-amanitin resistant mutants of the RNA polymerase II large subunit with slow elongation rates. Anti-pol II total nascent RNA sequencing (tNET-seq) was developed to assay transcription by WT and slow pol II. Slow pol II mutants in S. cerevisiae were also assayed for pol II CTD Ser2 phosphorylation.
Project description:Termination of Pol II transcription is an important step in the transcription cycle and is responsible for dislodgement of polymerase from DNA which leads to the release of a functional transcript. Recent studies have identified key players important for termination and showed a conserved domain that interacts with the phosphorylated C-terminus of Pol II (CTD-Interacting-Domain, CID) to constitute a common feature of these proteins. However, the mechanism by which transcription termination is achieved, is not understood. Using genome-wide methods, we demonstrate that the fission yeast CID protein Seb1 is essential for termination of protein-coding and non-coding genes through interacting with S2-phosphorylated Pol II and nascent RNA. Furthermore, we present the crystal structures of the Seb1 CTD- and RNA-binding modules. Unexpectedly, the latter reveals a novel intertwined two-domain arrangement of a canonical RRM and a second domain. These results provide important insights into the mechanism underlying eukaryotic transcription termination. Overall design: In this study, we studied binding of the S. pombe protein Seb1 directly to RNA by PAR-CLIP which was normalised to RNA expression levels (for which a RNA-Seq in WT cells was included). Point mutations were then introduced into Seb1 using a repressible system and RNA-Seq was performed for Seb1-WT and 5 different Seb1 point mutants that were all treated in the same way. Some samples were sequenced in duplicates and some (including the WT) in triplicates. Finally, binding was compared to another transcription factor, Pcf11, for which ChIP-Seq was performed. A control was done using an untagged strain. The binding profile was compared to phosphorylation levels of Ser2 on RNA-Pol II by doing ChIP-Seq for which an antibody against S2P was utilised. All ChIP-Seq experiments include an input sample.
Project description:CDK7 phosphorylates the RNA polymerase II (pol II) CTD and activates the P-TEFb- associated kinase, CDK9, but its regulatory roles remain obscure. Using human CDK7 analog-sensitive (CDK7as) cells, we observed reduced capping enzyme recruitment, increased pol II promoter-proximal pausing, and defective termination at gene 3'-ends upon CDK7 inhibition. We also found that CDK7 regulates chromatin modifications downstream of transcription start sites. H3K4me3 spreading was restricted at gene 5'-ends and H3K36me3 was displaced toward gene 3'-ends in CDK7as cells. Together, these results implicate a CDK7-dependent "CTD code" that regulates epigenetic marks in addition to RNA processing and pol II pausing. Overall design: WT and analogue sensitive Cdk7as mutant cells were treated with the ATP analogue NM-PP1 that specifically inhibits the Cdk7as mutant kinase. Using ChIP-seq and RNA-seq we tested the effects of Cdk7 inactivation on pol II distribution along genes, CTD Ser2 and Ser5 phosphorylation, capping enzyme recruitment, histone H3K4 and H3K36 methylation and mRNA expression
Project description:Transcription termination in Saccharomyces cerevisiae can be performed by at least two distinct pathways and is directed by the phosphorylation status of the carboxy-terminal domain (CTD) of RNA polymerase II (Pol II). Late termination of mRNAs is performed by the CPF/CF complex and requires CTD-Ser2 phosphorylation. Early termination of shorter cryptic unstable transcripts (CUTs) and small nucleolar RNAs (snoRNAs) is preformed by the Nrd1 complex, and requires CTD-Ser5 phosphorylation. In this study, mutants of the different termination pathways were compared by genome-wide expression analysis. Surprisingly, the expression changes observed upon loss of the CTD-Ser2 kinase Ctk1 are more similar to loss of a subunit of the Ser5P binding Nrd1-complex, than to loss of Ser2P binding factors. Tiling array analysis of ctk1Δ reveals readthrough at several hundred sites, including snoRNAs, as reported previously, but also many cryptic unstable transcripts, stable untranslated transcripts (SUTs) and other transcripts. Surprisingly, neither loss of CTK1 nor a Pol II CTD-Ser2 substitution mutant results in a global defect in termination of mRNAs, indicating that Ser2P is not essential for proper termination of most mRNAs. At snoRNA, Nrd1 location is shifted downstream in ctk1∆, indicating defective release rather than recruitment of Nrd1. Weakening the interaction between Nrd1 and Pol II rescues the readthrough in ctk1∆, likely by facilitating Nrd1 release. The termination defect is kinase activity dependent, but cannot be completely explained by loss of CTD-Ser2 phosphorylation , a major substrate of Ctk1, suggesting the involvement of an additional substrate. Mutant alleles of the elongation factor Spt5 rescue ctk1∆-dependent readthrough, indicating a role for Spt5 in this process, perhaps as a substrate of Ctk1. The results show that Ctk1 is more intimately involved in termination of small non-coding RNAs than was previously assumed and lead to a model in which Ctk1 influences Spt5 activity to achieve this. Two channel microarrays were used. RNA isolated from a large amount of wt yeast from a single culture was used as a common reference. This common reference was used in one of the channels for each hybridization and used in the statistical analysis to obtain an average expression-profile for each deletion mutant relative to the wt. Two independent cultures were hybridized on two separate microarrays. For the first hybridization the Cy5 (red) labeled cRNA from the deletion mutant is hybridized together with the Cy3 (green) labeled cRNA from the common reference. For the replicate hybridization, the labels are swapped. Each gene is represented twice on the microarray, resulting in four measurements per mutant. Using the Erlenmeyer growth protocol up to five deletion strains were grown on a single day. In the tecan platereader, up to eleven deletion strains could be grown on a single day. Wt cultures were grown parallel to the deletion mutants to assess day-to-day variance.