Project description:Determination of the 3' or 5' intragenic nascent transcriptional rate. Maintaining the proper mRNA levels is a key aspect in the regulation of gene expression. The balance between mRNA synthesis and decay determines these levels. Using a whole-genome analysis, we demonstrate that most yeast mRNAs are degraded by the 5'-to-3' pathway (the "decaysome"), as proposed previously. Unexpectedly, the level of these mRNAs is highly robust to perturbations in this major pathway, as defects in various decaysome components lead to transcription down-regulation. Moreover, these components shuttle between the cytoplasm and the nucleus, in a manner dependent on proper mRNA degradation. In the nucleus, they associate with chromatin - preferentially ~30bp upstream of transcription start-sites - and directly stimulate transcription initiation and elongation. Hence, the decaysome has a dual role in maintaining mRNA levels. Significantly, proper import of some decaysome components seems to play a key role in coupling the two functions. The gene expression process is therefore circular, whereby the hitherto first and last stages are interconnected.
Project description:Determination of the 3' or 5' intragenic nascent transcriptional rate. Maintaining the proper mRNA levels is a key aspect in the regulation of gene expression. The balance between mRNA synthesis and decay determines these levels. Using a whole-genome analysis, we demonstrate that most yeast mRNAs are degraded by the 5'-to-3' pathway (the "decaysome"), as proposed previously. Unexpectedly, the level of these mRNAs is highly robust to perturbations in this major pathway, as defects in various decaysome components lead to transcription down-regulation. Moreover, these components shuttle between the cytoplasm and the nucleus, in a manner dependent on proper mRNA degradation. In the nucleus, they associate with chromatin - preferentially ~30bp upstream of transcription start-sites - and directly stimulate transcription initiation and elongation. Hence, the decaysome has a dual role in maintaining mRNA levels. Significantly, proper import of some decaysome components seems to play a key role in coupling the two functions. The gene expression process is therefore circular, whereby the hitherto first and last stages are interconnected. This study focuses on the transcriptional activity of RNA pol II in the 3' or 5' region of 377 S. cerevisiae ORFs. S. cerevisiae cells grown in YPD to exponential phase were subjected to Genomic Run-On. Data were normalized using gDNA hybridized on the same array. Home-made macroarrays containing 300 bp from both the 5' or 3' ends of each ORF were used.
Project description:Determination of 3' or 5' intragenic RNA pol II occupancy. Maintaining the proper mRNA levels is a key aspect in the regulation of gene expression. The balance between mRNA synthesis and decay determines these levels. Using a whole-genome analysis, we demonstrate that most yeast mRNAs are degraded by the 5'-to-3' pathway (the "decaysome"), as proposed previously. Unexpectedly, the level of these mRNAs is highly robust to perturbations in this major pathway, as defects in various decaysome components lead to transcription down-regulation. Moreover, these components shuttle between the cytoplasm and the nucleus, in a manner dependent on proper mRNA degradation. In the nucleus, they associate with chromatin - preferentially ~30bp upstream of transcription start-sites - and directly stimulate transcription initiation and elongation. Hence, the decaysome has a dual role in maintaining mRNA levels. Significantly, proper import of some decaysome components seems to play a key role in coupling the two functions. The gene expression process is therefore circular, whereby the hitherto first and last stages are interconnected. This study focuses on the distribution of RNA pol II in the 3' or 5' region of 377 S. cerevisiae ORFs. S. cerevisiae cells grown in YPD to exponential phase were subjected to chromatin immunoprecipitation (ChIP) with anti-Rpb3 antibody. Data were normalized using whole cell extract hybridized on the same array. Home-made macroarrays containing 300 bp from both the 5' or 3' ends of each ORF were used.
Project description:Determination of 3' or 5' intragenic RNA pol II occupancy. Maintaining the proper mRNA levels is a key aspect in the regulation of gene expression. The balance between mRNA synthesis and decay determines these levels. Using a whole-genome analysis, we demonstrate that most yeast mRNAs are degraded by the 5'-to-3' pathway (the "decaysome"), as proposed previously. Unexpectedly, the level of these mRNAs is highly robust to perturbations in this major pathway, as defects in various decaysome components lead to transcription down-regulation. Moreover, these components shuttle between the cytoplasm and the nucleus, in a manner dependent on proper mRNA degradation. In the nucleus, they associate with chromatin - preferentially ~30bp upstream of transcription start-sites - and directly stimulate transcription initiation and elongation. Hence, the decaysome has a dual role in maintaining mRNA levels. Significantly, proper import of some decaysome components seems to play a key role in coupling the two functions. The gene expression process is therefore circular, whereby the hitherto first and last stages are interconnected.
Project description:In eukaryotic nuclei, most genes are transcribed by RNA polymerase II (RNAP2), whose regulation is a key to understanding the genome and cell function. RNAP2 has a long heptapeptide repeat (Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7), and Ser2 is phosphorylated on an elongation form. To detect RNAP2 Ser2 phosphorylation (RNAP2 Ser2ph) in living cells, we developed a genetically encoded modification-specific intracellular antibody (mintbody) probe. The RNAP2 Ser2ph-mintbody exhibited numerous foci, possibly representing transcription "factories," and foci were diminished during mitosis and in a Ser2 kinase inhibitor. An in vitro binding assay using phosphopeptides confirmed the mintbody's specificity. RNAP2 Ser2ph-mintbody foci were colocalized with proteins associated with elongating RNAP2 compared with factors involved in the initiation. These results support the view that mintbody localization represents the sites of RNAP2 Ser2ph in living cells. RNAP2 Ser2ph-mintbody foci showed constrained diffusional motion like chromatin, but they were more mobile than DNA replication domains and p300-enriched foci, suggesting that the elongating RNAP2 complexes are separated from more confined chromatin domains.
Project description:As RNA polymerase II (RNApII) transitions from initiation to elongation, Mediator and the basal transcription factors TFIID, TFIIA, TFIIH, and TFIIE remain at the promoter as part of a scaffold complex, whereas TFIIB and TFIIF dissociate. The yeast Ctk1 kinase associates with elongation complexes and phosphorylates serine 2 in the YSPTSPS repeats of the Rpb1 C-terminal domain, a modification that couples transcription to mRNA 3'-end processing. The higher eukaryotic kinase Cdk9 not only performs a similar function, but also functions at the 5'-end of genes in the transition from initiation to elongation. In strains lacking Ctk1, many basal transcription factors cross-link throughout transcribed regions, apparently remaining associated with RNApII until it terminates. Consistent with this observation, preinitiation complexes formed on immobilized templates with transcription extracts lacking Ctk1 leave lower levels of the scaffold complex behind after escape. Taken together, these results suggest that Ctk1 is necessary for the release of RNApII from basal transcription factors. Interestingly, this function of Ctk1 is independent of its kinase activity, suggesting a structural function of the protein.
Project description:RNA polymerase II (RNAPII) is the workhorse of eukaryotic transcription and produces messenger RNAs and small nuclear RNAs. Stalling of RNAPII caused by transcription obstacles such as DNA damage threatens functional gene expression and is linked to transcription-coupled DNA repair. To restore transcription, persistently stalled RNAPII can be disassembled and removed from chromatin. This process involves several ubiquitin ligases that have been implicated in RNAPII ubiquitylation and proteasomal degradation. Transcription by RNAPII is heavily controlled by phosphorylation of the C-terminal domain of its largest subunit Rpb1. Here, we show that the elongating form of Rpb1, marked by S2 phosphorylation, is specifically controlled upon UV-induced DNA damage. Regulation of S2-phosphorylated Rpb1 is mediated by SUMOylation, the SUMO-targeted ubiquitin ligase Slx5-Slx8, the Cdc48 segregase as well as the proteasome. Our data suggest an RNAPII control pathway with striking parallels to known disassembly mechanisms acting on defective RNA polymerase III.
Project description:mRNA homoeostasis is favoured by crosstalk between transcription and degradation machineries. Both the Ccr4-Not and the Xrn1-decaysome complexes have been described to influence transcription. While Ccr4-Not has been shown to directly stimulate transcription elongation, the information available on how Xrn1 influences transcription is scarce and contradictory. In this study we have addressed this issue by mapping RNA polymerase II (RNA pol II) at high resolution, using CRAC and BioGRO-seq techniques in Saccharomyces cerevisiae. We found significant effects of Xrn1 perturbation on RNA pol II profiles across the genome. RNA pol II profiles at 5' exhibited significant alterations that were compatible with decreased elongation rates in the absence of Xrn1. Nucleosome mapping detected altered chromatin configuration in the gene bodies. We also detected accumulation of RNA pol II shortly upstream of polyadenylation sites by CRAC, although not by BioGRO-seq, suggesting higher frequency of backtracking before pre-mRNA cleavage. This phenomenon was particularly linked to genes with poorly positioned nucleosomes at this position. Accumulation of RNA pol II at 3' was also detected in other mRNA decay mutants. According to these and other pieces of evidence, Xrn1 seems to influence transcription elongation at least in two ways: by directly favouring elongation rates and by a more general mechanism that connects mRNA decay to late elongation.
Project description:The cellular abundance of mature microRNAs (miRNAs) is dictated by the efficiency of nuclear processing of primary miRNA transcripts (pri-miRNAs) into pre-miRNA intermediates. The Microprocessor complex of Drosha and DGCR8 carries this out, but it has been unclear what controls Microprocessor's differential processing of various pri-miRNAs. Here, we show that Drosophila DGCR8 (Pasha) directly associates with the C-terminal domain of the RNA polymerase II elongation complex when it is phosphorylated by the Cdk9 kinase (pTEFb). When association is blocked by loss of Cdk9 activity, a global change in pri-miRNA processing is detected. Processing of pri-miRNAs with a UGU sequence motif in their apical junction domain increases, while processing of pri-miRNAs lacking this motif decreases. Therefore, phosphorylation of RNA polymerase II recruits Microprocessor for co-transcriptional processing of non-UGU pri-miRNAs that would otherwise be poorly processed. In contrast, UGU-positive pri-miRNAs are robustly processed by Microprocessor independent of RNA polymerase association.