Coactivator SAGA plays a crucial role in TBP recruitment for the Gcn4 transcriptome via subunits Spt3/Spt8
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PROVIDER: PRJNA1180110 | ENA |
REPOSITORIES: ENA
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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.
2025-07-16 | GSE280732 | GEO
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.
2025-07-16 | GSE295279 | GEO
Project description:Coactivator SAGA plays a crucial role in TBP recruitment for the Gcn4 transcriptome via subunits Spt3/Spt8 [RNA-seq]
| PRJNA1254112 | ENA
Project description:The SAGA coactivator complex facilitates transcription initiation through chromatin-modifying activities and interaction with TBP. SAGA was suggested to regulate the expression of about 10% of yeast genes, leading to the longstanding distinction of SAGA-dominated from TFIID-dominated genes, depending on the complex used to recruit TBP to promoters. We reassessed the genome-wide localization of SAGA by using ChEC-seq and its role on transcription through quantification of newly-synthesized mRNA. Here we show that SAGA binds to the upstream activating sequences of a majority of yeast genes. Deletion analyses reveal a global role for SAGA in transcription and a synergistic effect of Spt3 (TBP-binding subunit) with the acetyltransferase Gcn5. Our data demonstrate that SAGA acts as a general cofactor required for essentially all RNA polymerase II transcription. Hence, differential gene regulation, largely attributed to either SAGA or TFIID dominancy, is not accurate, but instead depends on other features of genes promoters.
2017-09-19 | GSE97379 | GEO
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.
2025-09-25 | GSE299870 | GEO
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.
2025-09-25 | GSE299866 | GEO
Project description:The SAGA complex is a conserved, multifunctional coactivator that plays broad roles in eukaryotic transcription. Previous studies suggested that Tra1, the largest SAGA component, is required either for SAGA assembly or for recruitment by DNA-bound transcriptional activators. In contrast to S. cerevisiae and mouse, a tra1? mutant is viable in S. pombe, allowing us to test these issues in vivo. We find that, in a tra1? mutant, SAGA assembles and is recruited to some, but not all promoters. Consistent with these findings, Tra1 regulates the expression of only a subset of SAGA-dependent genes. We previously reported that the SAGA subunits Gcn5 and Spt8 have opposing regulatory roles during S. pombe sexual differentiation. We show here that, like Gcn5, Tra1 represses this pathway, although by a distinct mechanism. Thus, our study reveals that Tra1 has specific regulatory roles, rather than global functions, within SAGA.
2011-06-13 | E-MTAB-678 | biostudies-arrayexpress
Project description:Co-activator complexes regulate chromatin accessibility and transcription. SAGA (Spt-Ada-Gcn5 Acetyltransferase) is an evolutionary conserved multisubunit co-activator complex with modular organization. The core module of SAGA constitutes the structural heart, composed of a histone octamer like structure and two additional proteins. The central histone octamer like core structure consists of six histone fold domain (HFD)-containing proteins, forming three HF pairs (TADA1/TAF12, TAF6L/TAF9/9b, and TAF10/SUPT7L) in the mammalian SAGA complexes, to which adds SUPT3H, which contains an intramolecular HF pair. The yeast homologue of SUPT3H, called Spt3, was shown to interact genetically and biochemically with the TATA binding protein (TBP). Here we investigated the role of SUPT3H in human U2OS and mouse embryonic stem (ES) cells. Using immuno-purification coupled mass spectrometry experiments we show that both human and mouse SAGA can assemble without the double HFD-containing SUPT3H. Nascent RNA-seq experiments indicted that in either U2OS or mouse ESCs lacking SUPT3H only a small subset of genes is deregulated. Consequently, in mouse ESCs SUPT3H is not essential for mouse ESC survival, but is required for ESC growth and self-renewal. In addition, TBP recruitment experiments show no major change in TBP accumulation at gene promoters in the absence of SUPT3H in mouse and human cells. Taken together our data suggest in mammalian cells SUPT3H is not required for the assembly of SAGA, general TBP recruitment to genes and cell survival, but it is important for regulating a limited set of genes.
2022-07-26 | PXD026991 | Pride
Project description:The SAGA complex is a conserved multifunctional coactivator known to play broad roles in eukaryotic transcription. To gain new insights into its functions, we have performed biochemical and genetic analyses of SAGA in the fission yeast, Schizosaccharomyces pombe. Purification of the S. pombe SAGA complex showed that its subunit composition is identical to that of Saccharomyces cerevisiae. Analysis of S. pombe SAGA mutants revealed that SAGA has two opposing roles regulating sexual differentiation. First, in nutrient rich conditions, the SAGA histone acetyltransferase, Gcn5, represses ste11+, which encodes the master regulator of the mating pathway. In contrast, the SAGA subunit Spt8 is required for the induction of ste11+ upon nutrient starvation. Chromatin immunoprecipitation experiments suggest that these regulatory effects are direct, as SAGA is physically associated with the ste11+ promoter independent of nutrient levels. Genetic tests suggest that nutrient levels do cause a switch in SAGA function, as spt8? suppresses gcn5? with respect to ste11+ derepression in rich medium, whereas the opposite relationship, gcn5? suppression of spt8?, occurs during starvation. Thus, SAGA plays distinct roles in the control of the switch from proliferation to differentiation in S. pombe through the dynamic and opposing activities of Gcn5 and Spt8.
2008-11-19 | E-MTAB-53 | biostudies-arrayexpress
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
2004-02-26 | E-GEOD-885 | biostudies-arrayexpress