Project description:ATP-dependent chromatin remodelers regulate chromatin structure during multiple stages of transcription. We report that RSC, an essential chromatin remodeler, is recruited to the open reading frames (ORFs) of actively transcribed genes genome-wide, suggesting a role for RSC in regulating transcription elongation. Consistent with such a role, Pol II occupancy in the ORFs of weakly transcribed genes is drastically reduced upon depletion of the RSC catalytic subunit Sth1. RSC inactivation also reduced histone H3 occupancy across transcribed regions. Remarkably, the strongest effects on Pol II and H3 occupancy were confined to the genes displaying the greatest RSC ORF enrichment. Additionally, RSC recruitment to the ORF requires the activities of the SAGA and NuA4 HAT complexes and is aided by the activities of the Pol II CTD Ser2 kinases Bur1 and Ctk1. Overall, our findings strongly implicate ORF-associated RSC in governing Pol II function and in maintaining chromatin structure over transcribed regions. ChIP-chip experiments to measure Sth1, Rpb3 and H3 occupancy in WT and various mutants (histone acetyltransferase and Pol II CTD kinase mutants). The histone H3 and Rpb3 occupancy were also measured in cells upon Sth1 depletion. The WT and mutant strains were grown in Synthetic complete or YPD media to an O.D. 600 of 0.6-0.8. For inducing Gcn4, the cells grown in SC were treated with Sulfometuron methyl for 20-25 minutes and process for chromatin immunoprecipitation using antibodies again Myc, Rpb3 or histone H3.
Project description:Cmr1 (changed mutation rate 1) is a largely uncharacterized nuclear protein that has recently emerged in several global genetic interaction and protein localization studies. It clusters with proteins involved in DNA damage and replication stress response, suggesting a role in maintaining genome integrity. Under conditions of proteasome inhibition or replication stress, this protein localizes to distinct sub-nuclear foci termed as intranuclear quality control (INQ) compartments, which sequester proteins for their subsequent degradation. Interestingly, it also interacts with histones, chromatin remodelers and modifiers, as well as with proteins involved in transcription including subunits of RNA Pol I and Pol III, but not with those of Pol II. It is not known whether Cmr1 plays a role in regulating transcription of Pol II target genes. Here, we show that Cmr1 is recruited to the coding regions of transcribed genes of S. cerevisiae. Cmr1 occupancy correlates with the Pol II occupancy genome-wide, indicating that it is recruited to coding sequences in a transcription-dependent manner. Cmr1-enriched genes include Gcn4 targets and ribosomal protein genes. Furthermore, our results show that Cmr1 recruitment to coding sequences is stimulated by Pol II CTD kinase, Kin28, and the histone deacetylases, Rpd3 and Hos2. Finally, our genome-wide analyses implicate Cmr1 in regulating Pol II occupancy at transcribed coding sequences. However, it is dispensable for maintaining co-transcriptional histone occupancy and histone modification (acetylation and methylation). Collectively, our results show that Cmr1 facilitates transcription by directly engaging with transcribed coding regions. ChIp-chip experiments were perfomed to determine genome-wide distribution of Cmr1 in WT and gcn4Î cells (S. cerevisiae). Rpb3 occupancy in WT and cmr1Î cells was also determined to reveal the changes in Pol II occupancy in the absence of Cmr1. The WT and mutant strains were grown in Synthetic complete and cells were indcued for Gcn4 by treating with Sulfometuron methyl for 30 minutes and processed for chromatin immunoprecipitation using antibodies against Myc and Rpb3 (subunit of Pol II).
Project description:ATP-dependent chromatin remodelers regulate chromatin structure during multiple stages of transcription. We report that RSC, an essential chromatin remodeler, is recruited to the open reading frames (ORFs) of actively transcribed genes genome-wide, suggesting a role for RSC in regulating transcription elongation. Consistent with such a role, Pol II occupancy in the ORFs of weakly transcribed genes is drastically reduced upon depletion of the RSC catalytic subunit Sth1. RSC inactivation also reduced histone H3 occupancy across transcribed regions. Remarkably, the strongest effects on Pol II and H3 occupancy were confined to the genes displaying the greatest RSC ORF enrichment. Additionally, RSC recruitment to the ORF requires the activities of the SAGA and NuA4 HAT complexes and is aided by the activities of the Pol II CTD Ser2 kinases Bur1 and Ctk1. Overall, our findings strongly implicate ORF-associated RSC in governing Pol II function and in maintaining chromatin structure over transcribed regions. In these experiments, we have analyzed Sth1 (catalytic subunit of the RSC chromatin remodeling complex) enrichment to the transcribing genes. The cells (WT and gcn4M-NM-^T) harboring STH1-MYC allele were treated by SM for 20 minutes to induce Gcn4 regulated genes. The chromatin extracts were prepared and subjected to chromatin immunoprecipitation using anti-Myc antibodies. The ChIP DNA as well the corresponding input DNA were biotinylated and hybridized to the Affymetrix tiling Arrays. Chromatin samples from two different cultures were used in this analysis.
Project description:Spt6 is a multifunctional histone chaperone involved in the maintenance of chromatin structure during elongation by RNA polymerase II (Pol II). Spt6 has a tandem SH2 (tSH2) domain within its C-terminus that recognizes Pol II CTD peptides phosphorylated on Ser2, Ser5 or Try1 in vitro. Deleting the tSH2 domain, however, only has a partial effect on Spt6 occupancy in vivo, suggesting that more complex mechanisms are involved in the Spt6 recruitment. Our results show that the Ser2 kinases Bur1 and Ctk1, but not the Ser5 kinase Kin28, cooperate in recruiting Spt6, genome-wide. Interestingly, the Ser2 kinases promote the association of Spt6 in early transcribed regions and not toward the 3' end of genes, where phosphorylated Ser2 reaches its maximum level. Additionally, our results uncover an unexpected role for histone deacetylases (Rpd3 and Hos2) in promoting Spt6 interaction with elongating Pol II. Finally, our data suggest that phosphorylation of the Pol II CTD on Tyr1 promotes the association of Spt6 with the 3' end of transcribed genes, independently of Ser2 phosphorylation. Collectively, our results show that a complex network of interactions, involving the Spt6 tSH2 domain, CTD phosphorylation and histone deacetylases, coordinate the recruitment of Spt6 to transcribed genes in vivo. We examined the genome-wide distribution (using ChIP-chip) of Spt6. Spt6 occupancy was also assayed in mutants for CTD Serine 2 and Serine 5 kinases and in mutants for histone deacetylases. ChIPs were performed with a Myc-tagged version of Spt6. Most ChIPs (in Cy5) were hybridyzed against a control ChIP sample from an isogenic non-tagged strain (in Cy3). In the ChIP experiments with the spt6-202del mutant, non immunoprecipitated DNA (input) was used as the control. In addition to Spt6 ChIPs, the project includes RNAPII (Rpb3) ChIP-chip datasets, where an anti-Rpb3 antibody was used to ChIP RNAPII and non immunoprecipitated DNA (input) was used as the control. All ChIP-chip experiments were done in duplicates. Each microarray was normalized using the Lima Loess and replicates were combined using a weighted average method as previously described (Pokholok et al., 2005).
Project description:Chaperones, nucleosome remodeling complexes and histone acetyltransferases have been implicated in nucleosome disassembly at promoters of particular yeast genes, but whether these co-factors function ubiquitously, and the impact of nucleosome eviction on transcription genome-wide, are poorly understood. We used chromatin immunoprecipitation of histone H3 and RNA polymerase II (Pol II) in mutants lacking single or multiple co-factors to address these issues for ~200 genes belonging to the Gcn4 transcriptome, of which ~70 exhibit marked reductions in H3 promoter occupancy on induction by amino acid starvation. Examining four target genes in a panel of mutants indicated that SWI/SNF, Gcn5, the Hsp70 co-chaperone Ydj1, and chromatin-associated factor Yta7 are required downstream of Gcn4 binding for robust H3 eviction in otherwise wild-type cells. Using ChIP-seq to interrogate all 70 exemplar genes in single, double and triple mutants implicated Gcn5, Snf2 and Ydj1 in H3 eviction at most, but not all Gcn4 target promoters, with Gcn5 generally playing the greatest role and Ydj1 the least. Remarkably, these 3 co-factors cooperate similarly in H3 eviction at virtually all yeast promoters. Defective H3 eviction in co-factor mutants was coupled with reduced Pol II occupancies for the Gcn4 transcriptome and the most highly expressed uninduced genes, but the relative Pol II levels at most genes were unaffected or even elevated. These findings indicate that nucleosome eviction is crucial for robust transcription of highly expressed genes, but that other steps in gene activation are more rate-limiting for most other yeast genes. Chromatin immunoprecipitated DNA from WT (induced(+SM) and uninduced(no SM)) and mutants (induced(+SM)) followed by paired-end sequencing. Nucleosomal DNA obtained by MNase digestion were also subjected to paired-end sequencing.
Project description:TFIID and SAGA complexes play a critical role in RNA Polymerase II dependent activated transcription. Although the two regulatory complexes are recruited to promoters by activation domain-interactions, the contribution of the different subunits or the different domains of the individual subunits is not completely understood. Taf9 is a shared subunit in TFIID and SAGA and has an N-terminal H3-like histone fold domain and a highly conserved C-terminal domain, Taf9-CTD. In this study, we have uncovered an essential role for the Taf9-CTD in transcriptional activation. The Taf9-CTD was not essential for the histone-fold mediated interaction with Taf6, SAGA and TFIID integrity or Gcn4 interaction with SAGA. Transcriptome profiling performed under Gcn4 activating conditions showed that the Taf9-CTD is required for expression of ~17% of the yeast genome and provides a coactivator function to recruit TFIID and SAGA complexes to the promoters in vivo during transcriptional activation. Integrated genome-wide data analysis showed that the Taf9-CTD is required for activation of promoters bound by several transcription factors indicating a broad role for Taf9-CTD in promoter occupancy of TFIID or SAGA complexes. Interestingly, only a subset of the promoters seemed to be dependent on the Taf9-CTD for assembly of the pre-initiation complex indicating redundancy in activator targets to assemble PIC in vivo. Together these results indicate that evolutionarily conserved domains in shared subunits of TFIID and SAGA have a pervasive role in genome-wide transcription. This GEO series consists of 14 microarray hybridizations using the Agilent two-color experiment with the Agilent Custom Saccharomyces cerevisiae 8x15k gene expression array. Four biological replicates each for the wild-type (TAF9), the mutant taf9-tCRD2 strain treated or untreated with SM, and the wild-type (TAF9) versus mutant taf9-tCRD2 treated with SM hybridized as dye-swapped replicates. Two biological replicates for wild-type (SPT20) vs spt20D strains treated with SM, and hybridized as dye-swapped replicates to identify the fraction of SAGA dependent genes under amino-acid starvation conditions. The overall aim was to identify genes dependent on the conserved C-terminal region domain of TAF9 and determine their dependence on the SAGA subunit Spt20 for expression.
Project description:RNA polymerase III transcribes many noncoding RNAs (e.g. tRNAs) important for translational capacity and other functions. Here, we localized RNA polymerase III, alternative TFIIIB complexes (BRF1/2) and TFIIIC in HeLa cells, determining the Pol III transcriptome, defining gene classes, and revealing ‘TFIIIC-only’ sites. Pol III localization in other transformed and primary cell lines revealed both novel and cell-type specific Pol III loci, and one occupied miRNA. Surprisingly, only a fraction of the in silico-predicted Pol III loci are occupied. Interestingly, many occupied Pol III genes reside within an annotated Pol II promoter. Outside of Pol II promoters, occupied Pol III genes overlap with enhancer-like chromatin and enhancer binding proteins such as ETS1 and STAT1. Remarkably, Pol III occupancy scales with the levels of nearby Pol II, active chromatin and CpG content. Taken together, active promoter and enhancer-like chromatin appears to gate Pol III accessibility to the genome. Use of ChIP-array to identify genomic regions bound by RNA Polymerase III machinery
Project description:Interactions between the nuclear lamina (NL) and chromatin are thought to occur through large lamin association domains (LADs) and correlate with gene repression in these domains. We show that binding of lamin A/C (LMNA) to promoters occurs on discrete domains that are associated with distinct transcriptional outputs. Chromatin immunoprecipitation identifies thousands of LMNA-bound promoters, primarily linked to signaling functions. LMNA often occupies narrow domains on promoters, yet LMNA-bound promoters are often contiguous. LMNA-bound genes are overall repressed, but repression correlates with co-enrichment in repressive histone marks rather than LMNA occupancy per se. Genes marked by LMNA and H3K4me3 escape LMNA-associated repression in the absence of repressive histone marks. Positioning of LMNA on promoters relative to the TSS correlates with distinct transcriptional outputs: whereas upstream-distal binding can be transcriptionally permissive, TSS occupancy is associated with promoter inactivity. Perturbation in NL organization causes reorganization of lamin promoter occupancy and uncouples LMNA binding from promoter inactivity. Our results show the existence of many spatially restricted LMNA binding events on promoter regions, with distinct position-dependent transcriptional outputs. ChIPs were done from cultured untreated and LMNA-downregulated adipose stem cell (ASC) chromatin. MeDIPs were done from LMNA-downregulated ASCs. ChIP and MeDIP DNA was hybridized onto the aforementioned HG-18 Nimbegen promoter arrays.
Project description:The Snf1 kinase plays a critical role in recalibrating cellular metabolism in response to glucose depletion. Hundreds of genes show changes in expression levels when the SNF1 gene is deleted. However, cells can adapt to the absence of a specific gene when grown in long term culture. Here we apply a chemical genetic method to rapidly and selectively inactivate a modified Snf1 kinase using a pyrazolopyrimidine inhibitor. By allowing cells to adjust to a change in carbon source prior to inhibition of the Snf1 kinase activity, we identified a set of genes whose expression increased when Snf1 was inhibited. Prominent in this set are genes that are activated by Gcn4, a transcriptional activator of amino acid biosynthetic genes. Deletion of Snf1 increased Gcn4 protein levels without affecting its mRNA levels. The increased Gcn4 protein levels required the Gcn2 kinase and Gcn20, regulators of GCN4 translation. These data indicate that Snf1 functions upstream of Gcn20 to regulate control of GCN4 translation. Experiment Overall Design: Strains growing in raffinose medium and expressing Snf1 and Snf1-I132G proteins were treated with a pyrazolopyrimidine inhibitor (2NM-PP1) to specifically inhibit Snf1-I132G kinase activity. RNA combined from three individual transformants were processed in duplicate for each strain, for a total analysis of four Affymetrix Yeast Genome S98 arrays.