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: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.
Project description:TFIID and SAGA are the only two known yeast complexes that modify chromatin and deliver TBP to promoters. Previous genome wide expression studies indicated that TFIID and SAGA positively regulate most but not all yeast genes. Using a relatively low noise microarray approach, we have re-examined the genome-wide dependence on TFIID and SAGA. We find that TFIID and SAGA contribute to the expression of virtually the entire genome, with TFIID being preferred at ~90% of the genes, and SAGA being preferred at ~10%. SAGA-dominated genes were found to overlap substantially with a previously described set of highly active genes that are attenuated in part by the TBP regulator NC2, and an auto-inhibitory function of TFIID. These SAGA-dominated genes also encompass most of the previously reported âTAF-independentâ genes. These results build upon and refine the generally held view that activators recruit either TFIID or SAGA to promoters which then bind and acetylate nucleosomes locally, thereby enhancing TBP delivery to the TATA box. Promoter-specific differences in the ability to alleviate auto-inhibitory activities associated with TFIID and SAGA might contribute to the preferential use one complex versus the other. Keywords = Chromatin Immunoprecipitation Keywords = genome-wide binding
Project description:Transcription initiation by RNA polymerase II is facilitated by coactivators that recruit general initiation factors to promoters. Coactivator complexes TFIID and SAGA recruit TATA-binding protein (TBP), while SAGA also enhances transcription by histone acetylation via the HAT Gcn5. It was proposed that most yeast genes depend exclusively on TFIID, with only ~10% requiring cumulative contributions by SAGA and TFIID for efficient transcription. It was further suggested that genes induced by Gcn4, transcriptional activator of amino acid biosynthetic genes induced by amino acid starvation, depend on the HAT but not the TBP-recruitment function of SAGA. At odds with this model, ChIP-sequencing of TBP and Pol II subunit Rpb1 revealed that deleting SPT3 or SPT8, but not GCN5, reduced TBP binding at many Gcn4 target genes. In contrast, deleting GCN5 but not SPT3 or SPT8 impaired promoter histone eviction at the highly remodeled subset of induced genes, whereas transcription was broadly reduced by all three SAGA mutations. Nuclear depletion of TFIID subunit Taf1 generally reduced TBP recruitment at these and most other SAGA-dependent genes only in cells lacking Spt3 or Spt8. We conclude that SAGA is crucial for TBP recruitment via Spt3/Spt8, beyond its role in histone acetylation, and functions non-redundantly with TFIID in the Gcn4 transcriptome of amino acid-starved cells.
Project description:Organisms respond to heat stress by reprogramming gene expression. Here we show that genome-wide reprogramming involves enhanced assembly of the TFIID and SAGA regulatory pathways at heat induced genes, and disassembly of the TFIID pathway at heat-repressed genes. While TFIID and SAGA are recruited to heat-induced genes, only SAGA appears to be associated with achieving maximal induction. Mot1, an ATP-dependent inhibitor of the TATA binding protein TBP, assembles at heat-induced SAGA-regulated genes, but functions to attenuate rather than promote activation. Changes in promoter occupancy of bromodomain factor Bdf1 are tightly linked to changes in TFIID occupancy, which further supports the notion that the two work together. Bdf1 is inhibitory to a number of SAGA-regulated genes and dissociates when these genes are activated, suggesting that Bdf1 normally blocks transcription complex assembly at these genes. These linkages in reprogramming of factor occupancy at promoters provide direct evidence for two functionally distinct transcription assembly pathways, and reveal unexpected cross-talk between the pathways. Keywords = Chromatin Immunoprecipitation Keywords = Microarray Keywords = TBP
Project description:Coactivator complexes TFIID and SAGA recruit TATA-binding protein (TBP), while SAGA also enhances transcription by histone acetylation via the HAT Gcn5. It was proposed that most yeast genes depend exclusively on TFIID, with only ~10% requiring cumulative contributions by SAGA and TFIID for efficient transcription. It was further suggested that genes induced by Gcn4, transcriptional activator of amino acid biosynthetic genes induced by amino acid starvation, depend on the HAT, but not TBP-recruitment function of SAGA. At odds with this model, ChIP-sequencing of TBP and Pol II subunit Rpb1 revealed that deleting SPT3 or SPT8, but not GCN5, reduced TBP binding at most Gcn4 target genes, whereas deleting GCN5 selectively impaired promoter histone eviction; and all three SAGA mutations reduced transcription comparably. Nuclear depletion of TFIID subunit Taf1 generally reduced TBP recruitment at these and most other SAGA-dependent genes only in cells lacking Spt3 or Spt8. We conclude that SAGA is crucial for TBP recruitment via Spt3/Spt8, beyond its role in histone acetylation, whereas TFIID plays an ancillary role for the Gcn4 transcriptome in amino acid-starved cells.
Project description:Mot1 is an essential Snf2-family ATPase in budding yeast that regulates transcription by dissociating the general initiation factor TBP (TATA-binding protein) from DNA. Previous studies showed that in optimum growth conditions Mot1 preferentially removes TBP from stress-responsive promoters that utilize the coactivator SAGA to enhance TBP binding at TFIID-dependent promoters of “housekeeping” genes. In stress conditions of amino acid starvation, by contrast, we found that Mot1 promotes high-level TBP occupancy at genes activated by transcription factor Gcn4, enriched for SAGA-dependent promoters, and at highly-transcribed subsets of constitutively expressed SAGA- and TFIID-dependent genes, while suppressing TBP occupancies at lowly transcribed genes regardless of SAGA/TFIID dependence. Importantly, the response to Mot1 depletion for genes induced by starvation or oxidative stress switched from decreased to increased TBP occupancies when transcribed at low basal levels in non-stressed cells. Notably, reduced TBP binding on Mot1 depletion impairs transcription of highly expressed TFIID genes but not highly expressed SAGA/stress-activated genes, implying that promoter activation by SAGA produces a surfeit of incomplete preinitiation complexes dependent on Mot1 for their formation.
Project description:Mot1 is an essential Snf2-family ATPase in budding yeast that regulates transcription by dissociating the general initiation factor TBP (TATA-binding protein) from DNA. Previous studies showed that in optimum growth conditions Mot1 preferentially removes TBP from stress-responsive promoters that utilize the coactivator SAGA to enhance TBP binding at TFIID-dependent promoters of “housekeeping” genes. In stress conditions of amino acid starvation, by contrast, we found that Mot1 promotes high-level TBP occupancy at genes activated by transcription factor Gcn4, enriched for SAGA-dependent promoters, and at highly-transcribed subsets of constitutively expressed SAGA- and TFIID-dependent genes, while suppressing TBP occupancies at lowly transcribed genes regardless of SAGA/TFIID dependence. Importantly, the response to Mot1 depletion for genes induced by starvation or oxidative stress switched from decreased to increased TBP occupancies when transcribed at low basal levels in non-stressed cells. Notably, reduced TBP binding on Mot1 depletion impairs transcription of highly expressed TFIID genes but not highly expressed SAGA/stress-activated genes, implying that promoter activation by SAGA produces a surfeit of incomplete preinitiation complexes dependent on Mot1 for their formation.
Project description:TFIID and SAGA share a common set of TAFs, regulate chromatin, and deliver TBP to promoters. Here we examine their relationship within the context of the Saccharomyces cerevisiae genome-wide regulatory network. We find that while TFIID and SAGA make overlapping contributions to the expression of all genes, TFIID function predominates at ~90% and SAGA at ~10% of the measurable genome. Strikingly, SAGA-dominated genes are largely stress-induced and TAF-independent, and are down-regulated by the coordinate action of a variety of chromatin, TBP, and RNA polymerase II regulators. In contrast, the TFIID-dominated class is less regulated, but is highly dependent upon TAFs including those shared between TFIID and SAGA. These two distinct modes of transcription regulation might reflect the need to balance inducible stress responses with the steady output of housekeeping genes. Keywords = Taf1 Keywords = Spt3 Keywords = Gcn5
Project description:TFIID and SAGA are the only two known yeast complexes that modify chromatin and deliver TBP to promoters. Previous genome wide expression studies indicated that TFIID and SAGA positively regulate most but not all yeast genes. Using a relatively low noise microarray approach, we have re-examined the genome-wide dependence on TFIID and SAGA. We find that TFIID and SAGA contribute to the expression of virtually the entire genome, with TFIID being preferred at ~90% of the genes, and SAGA being preferred at ~10%. SAGA-dominated genes were found to overlap substantially with a previously described set of highly active genes that are attenuated in part by the TBP regulator NC2, and an auto-inhibitory function of TFIID. These SAGA-dominated genes also encompass most of the previously reported “TAF-independent” genes. These results build upon and refine the generally held view that activators recruit either TFIID or SAGA to promoters which then bind and acetylate nucleosomes locally, thereby enhancing TBP delivery to the TATA box. Promoter-specific differences in the ability to alleviate auto-inhibitory activities associated with TFIID and SAGA might contribute to the preferential use one complex versus the other. Keywords = Chromatin Immunoprecipitation Keywords = genome-wide binding Keywords: other