Genome-wide mapping of yeast RNA polymerase II termination
ABSTRACT: Using a modification of the yeast anchor away and PAR-CLIP protocols, we have mapped the position of Pol II genome-wide in living yeast cells after depletion of components of either the polyadenylation (pA) or non-pA termination complexes. Depletion of Ysh1 from the nucleus does not lead to readthrough transcription. In contrast, depletion of the termination factor Nrd1 leads to widespread runaway elongation of non-pA transcripts. Depletion of Sen1 also leads to readthrough at non-pA terminators but in contrast to Nrd1 this readthrough appears less processive. Examination of PAR-CLIP sequencing data of Pol II after removal of different transcriptional termination factors.
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:Nuclear depletion of the essential transcription termination factor Nrd1 in Saccharomyces cerevisiae was studied using a combination of RNA-Seq, ChIP-Seq of Pol II and PAR-CLIP of Nrd1. The drug rapamycin induces the formation of a ternary complex between a protein of interest, the drug and the small subunit of the ribosome (both proteins are genetically engineered). The small ribosome subunit is transported out of the nucleus. therefore the protein of interest can be depleted from nucleus upon treatment with rapamycin.
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.
Project description:RNAPII is responsible for transcription of protein-coding genes and short, regulatory RNAs. In Saccharomyces cerevisiae, termination of RNAPII-transcribed RNAs ≤1000 bases requires the NNS complex (comprised of Nrd1, Nab3, and Sen1) processing by the exosome, and the nuclear specific catalytic subunit, Rrp6. It has been shown that Rrp6 interacts directly with Nrd1, but whether or not Rrp6 is required for NNS-dependent termination is unclear. Loss of Rrp6 function may result in extension (or inhibition of termination) of NNS-dependent transcripts, or Rrp6 may only function after the fact to carry out RNA 3’ end processing. Here, we performed in-depth differential expression analyses and compare RNA-sequencing data of transcript length and abundance in cells lacking RRP6 to previously published sequencing data measuring the length of RNAs in Nrd1-depleted cells. We find many transcripts that were defined as unterminated upon loss of Nrd1 activity are of similar length in rrp6Δ, and expression levels of downstream genes are significantly decreased. This suggests a similar transcription interference mechanism occurs in cells lacking either Nrd1 or Rrp6, supporting the hypothesis that Rrp6 activity is required for proper NNS termination in vivo. Four biological replicates each for deletion mutant (RRP6) and reference cells (WT)
Project description:RNA Polymerase II (RNAPII) termination for transcripts containing a polyadenylation signal (PAS) is thought to differ mechanistically from termination for PAS-independent RNAPII transcripts such as sn(o)RNAs. In a screen for factors required for PAS-dependent termination, we identified Sen1, a putative helicase known primarily for its role in PAS-independent termination. We show that Sen1 is required for termination on hundreds of protein-coding genes and suppresses cryptic transcription from nucleosome-free regions on a genomic scale. These effects often overlap with but are also often distinct from those caused by Nrd1 depletion, which also impacts termination of protein-coding and cryptic transcripts, including many genic antisense transcripts. Sen1 controls termination through its helicase activity and stimulates recruitment of factors previously implicated in both PAS-dependent (Rna14, Rat1) and PAS-independent (Nrd1) termination. Thus, RNAPII termination for both protein-coding genes and cryptic transcripts is dependent on multiple pathways. Overall design: The 2 RNAPII datasets were produced in duplicates and the Sen1 and Nrd1 datasets in triplicates (all IP/Input).
Project description:At the end of protein-coding genes, RNA polymerase (Pol) II undergoes a concerted transition that involves 3’-processing of the pre-mRNA and transcription termination. Here we conduct a genome-wide analysis of this 3’-transition in yeast. We find that the 3’-transition globally requires the Pol II elongation factor Spt5 and factors involved in the recognition of the poly-adenylation (pA) site and in endonucleolytic RNA cleavage. Pol II release from DNA occurs in a narrow termination window downstream of the pA site and generally requires the ‘torpedo’ exonuclease Rat1 (human XRN2). The Rat1-interacting factor Rai1 contributes to RNA degradation downstream of the pA site. Defects in the 3’-transition result in transcription interference at downstream genes, which is attenuated by a back-up termination mechanism. Overall design: In this study, we depleted the main termination factors of the Rat1–Rai1–Rtt103 exonuclease complex as well as the CFIA factor Pcf11 from the nucleus and monitored changes in RNA synthesis using the anchor-away (aa) technique and 4-thiouracil (4tU) sequencing, respectively. We applied ChIP-seq and PAR-CLIP to obtain high-confidence genome and transcriptome maps, respectively. Additionally, we assayed the effects after nuclear depletion of Spt4/5 as well as for Spt5 mutants lacking both the C-terminal repeat (CTR) and fifth KOW domain. We show that Rat1 is needed for termination of the transcribing RNA Polymerase (Pol) II by comparing the ChIP-seq profiles of Rpb1 before (Rat1no) and after nuclear depletion (Rat1aa) of the exonculease Rat1.
Project description:RNA Polymerase II (RNAPII) termination for transcripts containing a polyadenylation signal (PAS) is thought to differ mechanistically from termination for PAS-independent RNAPII transcripts such as sn(o)RNAs. In a screen for factors required for PAS-dependent termination, we identified Sen1, a putative helicase known primarily for its role in PAS-independent termination. We show that Sen1 is required for termination on hundreds of protein-coding genes and suppresses cryptic transcription from nucleosome-free regions on a genomic scale. These effects often overlap with but are also often distinct from those caused by Nrd1 depletion, which also impacts termination of protein-coding and cryptic transcripts, including many genic antisense transcripts. Sen1 controls termination through its helicase activity and stimulates recruitment of factors previously implicated in both PAS-dependent (Rna14, Rat1) and PAS-independent (Nrd1) termination. Thus, RNAPII termination for both protein-coding genes and cryptic transcripts is dependent on multiple pathways. The 2 RNAPII datasets were produced in duplicates and the Sen1 and Nrd1 datasets in triplicates (all IP/Input).
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:We report here the transcriptome-wide distribution of yeast Rpb2, Sen1, Nrd1 and Nab3 binding sites. These data sets provide highresolution definition of non-poly(A) terminators, identify novel genes regulated by attenuation of nascent transcripts close to the promoter, and demonstrate the widespread occurrence of Nrd1-bound 3'-antisense transcripts on genes that are poorly expressed. In addition, we show that Sen1 does not cross-link to many expected ncRNAs but surprisingly binds to pre-mRNA transcripts suggesting a role in 3' end formation and/or termination. Six samples by adaptation of PAR-ClIP procedure
Project description:Termination of yeast RNA polymerase II (Pol II) transcripts occurs through two alternative pathways. Termination of mRNAs is coupled to cleavage and polyadenylation while non-coding transcripts are terminated through the Nrd1-Nab3-Sen1 (NNS) pathway in a process that is linked to RNA degradation by the nuclear exosome. Some mRNA transcripts are also attenuated through premature termination directed by the NNS complex. In this paper we present the results of nuclear depletion of the NNS component Nab3. As expected many non-coding RNAs fail to terminate properly. In addition, we observe that nitrogen catabolite repressed genes are up-regulated by Nab3 depletion. Overall design: Yeast Pol II genome wide positioning before and after Nab3-FRB tagged nuclear depletion using Illumina HI-Seq