Project description:Genome-wide studies have identified abundant small, non-coding RNAs including snRNAs, snoRNAs, cryptic unstable transcripts (CUTs), and upstream regulatory RNAs (uRNAs) that are transcribed by RNA polymerase II (pol II) and terminated by a Nrd1-dependent pathway. Here, we show that the prolyl isomerase, Ess1, is required for Nrd1-dependent termination of ncRNAs. Ess1 binds the carboxy terminal domain (CTD) of pol II and is thought to regulate transcription by conformational isomerization of Ser-Pro bonds within the CTD. In ess1 mutants, expression of ~10% of the genome was altered, due primarily to defects in termination of snoRNAs, CUTs, SUTs and uRNAs. Ess1 promoted dephosphorylation of Ser5 (but not Ser2) within the CTD, most likely by the Ssu72 phosphatase, and we provide evidence for a competition between Nrd1 and Pcf11 for CTD-binding that is regulated by Ess1-dependent isomerization. This is the first example of a prolyl isomerase required for interpreting the “CTD code.”
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: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: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.
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.
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.
Project description:Termination of RNAPII transcription is associated with RNA 3â end formation. For coding genes, termination is initiated by the cleavage/polyadenylation machinery. In contrast, a majority of noncoding transcription events in S. cerevisiae do not rely on RNA cleavage for termination, but instead terminate via a pathway that requires the Nrd1-Nab3-Sen1 (NNS) complex. Here we show that the S. pombe ortholog of Nrd1, Seb1, does not function in NNS-like termination, but promotes polyadenylation site selection of coding and noncoding genes. We found that Seb1 associates with 3â end processing factors, is enriched at the 3â end of genes, and binds RNA motifs downstream of cleavage sites. Importantly, a deficiency in Seb1 resulted in widespread changes in 3â UTR length as a consequence of increased alternative polyadenylation. Given that Seb1 levels affected the recruitment of conserved 3â end processing factors, our findings indicate that the conserved RNA-binding protein Seb1 co-transcriptionally controls alternative polyadenylation. Two biological replicates of Seb1 and Control (parental strain) CRAC experiments
Project description:Transcription termination is key to gene regulation as it prevents transcription interference with neighboring genes. In Saccharomyces cerevisiae, termination at protein-coding genes is coupled to the cleavage of the nascent transcript, while most non-coding RNA transcription relies on a cleavage-independent termination pathway involving Nrd1, Nab3 and the helicase Sen1 (NNS pathway). In both pathways, the recruitment of termination factors involves phosphorylated forms of the RNA polymerase II C-terminal domain (CTD) but the contribution of individual CTD residues was never systematically investigated. Here, we investigated the impact of mutating phosphorylation sites in the CTD on termination. We observed widespread termination defects at protein-coding genes in mutants for Ser2 or Thr4 but rare defects in Tyr1 mutants for this class of genes. Instead, mutating Tyr1, or its phosphatase Glc7, led to widespread termination defects at non-coding genes known to terminate via the NNS pathway. These defects can be suppressed by slowing down transcription, suggesting that Tyr1 mediates termination via the regulation of elongation or pausing. Our work redefines the role of Tyr1 in termination at protein-coding genes in budding yeast and highlights its key role in termination by the NNS pathway.
Project description:Transcription termination is key to gene regulation as it prevents transcription interference with neighboring genes. In Saccharomyces cerevisiae, termination at protein-coding genes is coupled to the cleavage of the nascent transcript, while most non-coding RNA transcription relies on a cleavage-independent termination pathway involving Nrd1, Nab3 and the helicase Sen1 (NNS pathway). In both pathways, the recruitment of termination factors involves phosphorylated forms of the RNA polymerase II C-terminal domain (CTD) but the contribution of individual CTD residues was never systematically investigated. Here, we investigated the impact of mutating phosphorylation sites in the CTD on termination. We observed widespread termination defects at protein-coding genes in mutants for Ser2 or Thr4 but rare defects in Tyr1 mutants for this class of genes. Instead, mutating Tyr1, or its phosphatase Glc7, led to widespread termination defects at non-coding genes known to terminate via the NNS pathway. These defects can be suppressed by slowing down transcription, suggesting that Tyr1 mediates termination via the regulation of elongation or pausing. Our work redefines the role of Tyr1 in termination at protein-coding genes in budding yeast and highlights its key role in termination by the NNS pathway.
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.