Project description:The SAGA coactivator complex acts on the whole transcribed genome and is required for RNA polymerase II transcription [Yeast cells]
Project description:We have analyzed the global effect of the conserved transcription-mRNA export factor Sus1 on transcription and its association with chromatin. We used genomic run-on experiments to show that Sus has a broad impact on the stability of most RNA polymerase II-transcribed genes. Genome association of Sus1 by the chromatin immunoprecipitation technique showed that Sus1 was widely distributed throughout coding regions, tending to accumulate towards the 3â ends of highly transcribed transcription factor IID (TFIID) and Spt-Ada-Gcn5 acetyltransferase (SAGA) dependent genes. This accumulation depends on growth conditions, the transcriptional rate and whether the genes are TFIID- or SAGA-regulated. Validation of Sus1 occupancy data also revealed that Sus1 appears at tRNAs. Concomitantly, deletion of SUS1 leads to tRNA overexpression. In addition, we discovered that distinctive SAGA subunits Spt8 and Spt7 play a key role in Sus1 enrichment at the 3â ends of SAGA-regulated genes upon temperature shift and at tRNAs. Thus, our study identifies the molecular mechanisms by which a SAGA factor is recruited genome-wide, and provides evidence of a more general role for this conserved coactivator in eukaryotic transcription. Genome wide analysis of Sus1 in wild type and Spt7 and Spt8 deletion mutants using ChIP-exo and genomic run-on experiments
Project description:The SAGA co-activator complex contains distinct chromatin-modifying activities and is recruited by DNA-bound activators to regulate the expression of a subset of genes. Surprisingly, recent studies revealed little overlap between genome-wide SAGA-binding profiles and changes in gene expression upon depletion of subunits of the complex. As indicators of SAGA recruitment on chromatin, we monitored in yeast and human cells the genome-wide distribution of histone H3K9 acetylation and H2B ubiquitination, which are respectively deposited or removed by SAGA. Changes in these modifications after inactivation of the corresponding enzyme revealed that SAGA acetylates the promoters and deubiquitinates the transcribed region of all expressed genes. In agreement with this broad distribution, we show that SAGA plays a critical role for RNA polymerase II recruitment at all expressed genes. In addition, through quantification of newly synthesized RNA, we demonstrated that SAGA inactivation induced a strong decrease of mRNA synthesis at all tested genes. Analysis of the SAGA deubiquitination activity further revealed that SAGA acts on the whole transcribed genome in a very fast manner indicating a highly dynamic association of the complex with chromatin. Thus, our study uncovers a new function for SAGA as a bone fide co-factor for all RNA Polymerase II transcription. Comparison of H3K9ac, H2Bub and RNA Pol II distributions in WT yeast cells and upon the loss of SAGA activities.
Project description:We have analyzed the global effect of the conserved transcription-mRNA export factor Sus1 on transcription and its association with chromatin. We used genomic run-on experiments to show that Sus has a broad impact on the stability of most RNA polymerase II-transcribed genes. Genome association of Sus1 by the chromatin immunoprecipitation technique showed that Sus1 was widely distributed throughout coding regions, tending to accumulate towards the 3’ ends of highly transcribed transcription factor IID (TFIID) and Spt-Ada-Gcn5 acetyltransferase (SAGA) dependent genes. This accumulation depends on growth conditions, the transcriptional rate and whether the genes are TFIID- or SAGA-regulated. Validation of Sus1 occupancy data also revealed that Sus1 appears at tRNAs. Concomitantly, deletion of SUS1 leads to tRNA overexpression. In addition, we discovered that distinctive SAGA subunits Spt8 and Spt7 play a key role in Sus1 enrichment at the 3’ ends of SAGA-regulated genes upon temperature shift and at tRNAs. Thus, our study identifies the molecular mechanisms by which a SAGA factor is recruited genome-wide, and provides evidence of a more general role for this conserved coactivator in eukaryotic transcription.
Project description:The SAGA co-activator complex contains distinct chromatin-modifying activities and is recruited by DNA-bound activators to regulate the expression of a subset of genes. Surprisingly, recent studies revealed little overlap between genome-wide SAGA-binding profiles and changes in gene expression upon depletion of subunits of the complex. As indicators of SAGA recruitment on chromatin, we monitored in yeast and human cells the genome-wide distribution of histone H3K9 acetylation and H2B ubiquitination, which are respectively deposited or removed by SAGA. Changes in these modifications after inactivation of the corresponding enzyme revealed that SAGA acetylates the promoters and deubiquitinates the transcribed region of all expressed genes. In agreement with this broad distribution, we show that SAGA plays a critical role for RNA polymerase II recruitment at all expressed genes. In addition, through quantification of newly synthesized RNA, we demonstrated that SAGA inactivation induced a strong decrease of mRNA synthesis at all tested genes. Analysis of the SAGA deubiquitination activity further revealed that SAGA acts on the whole transcribed genome in a very fast manner indicating a highly dynamic association of the complex with chromatin. Thus, our study uncovers a new function for SAGA as a bone fide co-factor for all RNA Polymerase II transcription. Comparison of H3K9ac and H2Bub distributions in control HeLa cells and upon the inactivation of SAGA enzymatic activities