Project description:Increasing evidence supports that the activity of RNA polymerase II (RNA pol II) during transcription elongation can be regulated to control transcription rates. Using genomic run-on (GRO) and RNA pol II chromatin immunoprecipitation (RPCC), we have respectively measured active and total RNA pol II present in the body of genes at 3 different stages of the mitotic cell cycle of Saccharomyces cerevisiae: G1, S and G2/M. Comparison of active and total RNA pol II values at these three points defined several gene clusters that reflect different patterns of transcription elongation control across the cell cycle. Previously defined cycling genes were overrepresented in some of these clusters, which showed cyclic average mRNA expression patterns. One of the clusters with most divergent GRO and RPCC patterns was significantly enriched in genes functionally related to ribosome biogenesis (RiBi). We confirmed that RiBi mRNA expression upregulates after START. Finally, we analysed the contribution of mRNA stability to each cluster and found that concerted control of RNA pol II activity and mRNA decay is needed to fully understand alternative strategies of gene expression across the cell cycle.
Project description:During translation elongation, the ribosome ratchets along its mRNA template, incorporating each new amino acid and translocating from one codon to the next. The elongation cycle requires dramatic structural rearrangements of the ribosome. We show here that deep sequencing of ribosome-protected mRNA fragments reveals not only the position of each ribosome but also, unexpectedly, its particular stage of the elongation cycle. Sequencing reveals two distinct populations of ribosome footprints, 28-30 nucleotides and 20-22 nucleotides long, representing translating ribosomes in distinct states, differentially stabilized by specific elongation inhibitors. We find that the balance of small and large footprints varies by codon and is correlated with translation speed. The ability to visualize conformational changes in the ribosome during elongation, at single-codon resolution, provides a new way to study the detailed kinetics of translation and a new probe with which to identify the factors that affect each step in the elongation cycle. Ribosome profiling, or sequencing of ribosome-protected mRNA fragments, in yeast. We assay ribosome footprint sizes and positions in three conditions: untreated yeast (3 replicates) and yeast treated with translation inhibitors cycloheximide (2 replicates) and anisomycin (2 biological replicates, one technical replicate). We also treat yeast with 3-aminotriazole to measure the effect of limited histidine tRNAs on ribosome footprint size and distribution (two treatment durations).
Project description:Influence of a C-terminal deletion of the RNA polymerase II elongation factor Spt6 on the transcription of the yeast genome. In parallel the influence of a Spt6 overexpression on gene expression is analyzed.
Project description:RNA polymerase II (Pol II) elongation is a critical step in gene expression. Here we find that NDF, which was identified as a bilaterian nucleosome-destabilizing factor, is also a Pol II transcription factor that stimulates elongation with plain DNA templates in the absence of nucleosomes. NDF binds directly to Pol II and enhances elongation by a different mechanism than does transcription factor TFIIS. Moreover, yeast Pdp3, which is related to NDF, binds to Pol II and stimulates elongation. Thus, NDF is a Pol II-binding transcription elongation factor that is localized over gene bodies and is conserved from yeast to humans.
Project description:Transcription elongation rates influence RNA processing, but sequence-specific regulation is poorly understood. We addressed this in vivo, analyzing RNAPI in S. cerevisiae. Mapping RNAPI by Miller chromatin spreads or UV crosslinking revealed 5′ enrichment and strikingly uneven local polymerase occupancy along the rDNA, indicating substantial variation in transcription speed. Two features of the nascent transcript correlated with RNAPI distribution: folding energy and GC content in the transcription bubble. In vitro experiments confirmed that strong RNA structures close to the polymerase promote forward translocation and limit backtracking, whereas high GC in the transcription bubble slows elongation. A mathematical model for RNAPI elongation confirmed the importance of nascent RNA folding in transcription. RNAPI from S. pombe was similarly sensitive to transcript folding, as were S. cerevisiae RNAPII and RNAPIII. For RNAPII, unstructured RNA, which favors slowed elongation, was associated with faster cotranscriptional splicing and proximal splice site use, indicating regulatory significance for transcript folding.
Project description:RNA polymerase II promoter-proximal pausing is orchestrated by a ribonucleoprotein complex scaffolded by the noncoding RNA Rn7sk. However, how this interruption of transcription is mechanistically linked to RNA production remains largely unknown. Here, we show that forcing the pause release by germ-line deletion of Rn7sk was embryonic lethal, yet conditional deletion of Rn7sk enhanced stem cell differentiation in skin. To explore the immediate transcriptional mechanisms underpinning enhanced differentiation, we metabolically labelled newly-synthesized RNAs after Rn7sk deletion. Unexpectedly, forced pause release robustly repressed transcription specifically at cell cycle regulators, in the absence of chromatin remodeling at promoters and enhancers. Our results indicate that polymerase pausing affords the core elongation machinery time to properly assemble, and forced elongation triggers splicing defects and nuclear RNA decay. Cell cycle regulators appear highly sensitive to mis-regulation of the elongation machinery due to unique genomic features of high promoter accessibility and low GC–content in the gene body. Transcriptional pausing thus serves as a rate-limiting step in controlling cell division.
Project description:RNA polymerase II promoter-proximal pausing is orchestrated by a ribonucleoprotein complex scaffolded by the noncoding RNA Rn7sk. However, how this interruption of transcription is mechanistically linked to RNA production remains largely unknown. Here, we show that forcing the pause release by germ-line deletion of Rn7sk was embryonic lethal, yet conditional deletion of Rn7sk enhanced stem cell differentiation in skin. To explore the immediate transcriptional mechanisms underpinning enhanced differentiation, we metabolically labelled newly-synthesized RNAs after Rn7sk deletion. Unexpectedly, forced pause release robustly repressed transcription specifically at cell cycle regulators, in the absence of chromatin remodeling at promoters and enhancers. Our results indicate that polymerase pausing affords the core elongation machinery time to properly assemble, and forced elongation triggers splicing defects and nuclear RNA decay. Cell cycle regulators appear highly sensitive to mis-regulation of the elongation machinery due to unique genomic features of high promoter accessibility and low GC–content in the gene body. Transcriptional pausing thus serves as a rate-limiting step in controlling cell division.
Project description:After transcription initiation, RNA polymerase (Pol) II escapes from the promoter and recruits elongation factors. Here we used chromatin immunoprecipitation (ChIP) to elucidate the general initiation-elongation transition of Pol II in yeast. We extended our ChIP-chip occupancy profiling to capping enzymes and the cap-binding complex (CBC). We found that the first two capping enzymes, Cet1 and Ceg1, are recruited near the TSS, whereas the third enzyme, the methyltransferase Abd1, is recruited about 110 nt downstream of the TSS, and CBC is recruited further downstream. ChIP was performed using TAP-tagged S. cerevisiae strains (see protocols).
Project description:During translation elongation, the ribosome ratchets along its mRNA template, incorporating each new amino acid and translocating from one codon to the next. The elongation cycle requires dramatic structural rearrangements of the ribosome. We show here that deep sequencing of ribosome-protected mRNA fragments reveals not only the position of each ribosome but also, unexpectedly, its particular stage of the elongation cycle. Sequencing reveals two distinct populations of ribosome footprints, 28-30 nucleotides and 20-22 nucleotides long, representing translating ribosomes in distinct states, differentially stabilized by specific elongation inhibitors. We find that the balance of small and large footprints varies by codon and is correlated with translation speed. The ability to visualize conformational changes in the ribosome during elongation, at single-codon resolution, provides a new way to study the detailed kinetics of translation and a new probe with which to identify the factors that affect each step in the elongation cycle.
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