Project description:Mot1 is an essential TATA-binding protein (TBP)-associated factor and Snf2/Swi2 ATPase that both represses and activates transcription. Biochemical and structural results support a model in which ATP binding and hydrolysis induce a conformational change in Mot1 that drives local translocation along DNA, thus removing TBP. While this activity explains transcriptional repression, it does not as easily explain Mot1-mediated transcriptional activation, and several different models have been proposed to explain how Mot1 activates transcription. To better understand the function of Mot1 in yeast cells in vivo, particularly with regard to gene activation, TBP mutants were identified that bypass the requirement for Mot1 in vivo. Although TBP has been extensively mutated and analyzed previously, this screen uncovered two novel TBP variants that are unique in their ability to bypass the requirement for Mot1. Surprisingly, in vitro analyses reveal that rather than having acquired an improved biochemical activity, one of the TBPs was defective for interaction with Pol II preinitiation complex (PIC) components and other regulators of TBP function. The other mutant was defective for DNA binding in vitro, yet was still recruited to chromatin in vivo. These results suggest that Mot1-mediated dissociation of TBP (or TBP-containing complexes) from chromatin can explain the Mot1 activation mechanism at some promoters. The results also suggest that PICs can be dynamically unstable, and that appropriate PIC instability is critical for the regulation of transcription in vivo.
Project description:The Swi2/Snf2-family ATPase Mot1 displaces TBP from DNA in vitro, but the global relationship between Mot1 and TBP in vivo has been unclear. We therefore mapped the distribution of Mot1 and TBP on native chromatin at base-pair resolution. Mot1 and TBP binding sites coincide throughout the genome, and depletion of TBP results in a global decrease in Mot1 binding. Using midpoint-versus-length mapping to assess the spatial relationship of Mot1 and TBP on chromatin, we find evidence that Mot1 approaches TBP from the upstream direction, consistent with its in vitro mode of action. Strikingly, inactivation of Mot1 leads to both increases and decreases in TBP-genome association. Sites of TBP gain tend to contain robust TATA boxes, while sites of TBP loss contain poly(dA:dT) tracts that may contribute to nucleosome exclusion. We propose that the action of Mot1 is required to clear TBP from intrinsically preferred (TATA-containing) binding sites, ensuring sufficient soluble TBP to bind intrinsically disfavored (TATA-less) sites. We have analyzed the genomic distributions of yeast TBP and Mot1 using Occupied Regions of Genomes from Affinity-purified Naturally Isolated Chromatin and sequencing (ORGANIC-seq).
Project description:The Swi2/Snf2-family ATPase Mot1 displaces TBP from DNA in vitro, but the global relationship between Mot1 and TBP in vivo has been unclear. We therefore mapped the distribution of Mot1 and TBP on native chromatin at base-pair resolution. Mot1 and TBP binding sites coincide throughout the genome, and depletion of TBP results in a global decrease in Mot1 binding. Using midpoint-versus-length mapping to assess the spatial relationship of Mot1 and TBP on chromatin, we find evidence that Mot1 approaches TBP from the upstream direction, consistent with its in vitro mode of action. Strikingly, inactivation of Mot1 leads to both increases and decreases in TBP-genome association. Sites of TBP gain tend to contain robust TATA boxes, while sites of TBP loss contain poly(dA:dT) tracts that may contribute to nucleosome exclusion. We propose that the action of Mot1 is required to clear TBP from intrinsically preferred (TATA-containing) binding sites, ensuring sufficient soluble TBP to bind intrinsically disfavored (TATA-less) sites.
Project description:The majority of Saccharomyces cerevisiae snoRNA promoters contain an aRCCCTaa sequence motif located at the upstream border of a TATA-containing nucleosome-free region. Genome-wide ChIP-seq analysis showed that these motifs are bound in vivo by Tbf1, a telomere-binding protein known to recognize mammalian-like T2AG3 repeats at sub-telomeric regions. Tbf1 has over 100 additional promoter targets, including the TBF1 gene itself. Tbf1 is required for full snoRNA expression, yet it does not influence nucleosome positioning at snoRNA promoters.
Project description:The majority of Saccharomyces cerevisiae snoRNA promoters contain an aRCCCTaa sequence motif located at the upstream border of a TATA-containing nucleosome-free region. Genome-wide ChIP-seq analysis showed that these motifs are bound in vivo by Tbf1, a telomere-binding protein known to recognize mammalian-like T2AG3 repeats at sub-telomeric regions. Tbf1 has over 100 additional promoter targets, including the TBF1 gene itself. Tbf1 is required for full snoRNA expression, yet it does not influence nucleosome positioning at snoRNA promoters. Analysis of Tbf1-binding sites in Saccharomyces cerevisiae by ChIP-seq of a Myc-tagged strain and a control untagged strain. 1 sample per strain, 1 lane per sample.
Project description:TATA-binding protein (TBP) is central to the regulation of transcription initiation. Recruitment of TBP to target genes can be positively regulated by one of two basal transcription factor complexes: SAGA or TFIID. Negative regulation of TBP promoter association can be performed by Mot1 or the NC2 complex. Recent evidence suggest that Mot1, NC2, and TBP form a DNA-dependent protein complex. Here, we compare the functions of Mot1 and NC2beta during basal and activated transcription using the anchor-away technique for conditional nuclear depletion. Genome-wide expression analysis indicates that both proteins regulate a highly similar set of genes (r2=0.8). Upregulated genes were enriched for SAGA occupancy, while downregulated genes preferred TFIID binding. Mot1p and NC2beta depletion during heat shock resulted in a failure to downregulate gene expression after initial activation, which was accompanied by increased TBP and RNA pol II promoter occupancies. Depletion of Mot1p or NC2beta displayed preferential synthetic lethality with the TBP-interaction module of SAGA. Our results suggest that Mot1 and NC2beta cooperate in vivo to regulate TBP function, and that they are involved in maintaining basal expression levels as well as in resetting gene expression after induction by stress.
Project description:Mot1 is a conserved and essential Swi2/Snf2 ATPase that can remove TATA-binding protein (TBP) from DNA using ATP hydrolysis, and in so doing exerts global effects on transcription. Spt16 is also essential and functions globally in transcriptional regulation as a component of the FACT histone chaperone complex. Here we demonstrate that Mot1 and Spt16 regulate a largely overlapping set of genes in Saccharomyces cerevisiae. As expected, Mot1 was found to control TBP levels at co-regulated promoters. In contrast, Spt16 did not affect TBP recruitment. Interestingly, Mot1 was required for Spt16 recruitment to co-activated promoters. In contrast, Spt16 levels in gene coding regions were unaffected by Mot1 as well as RNA polymerase II density. The co-localization of Mot1 and Spt16 at promoters and the broad overlap in the sets of genes they control is consistent with physical and genetic interactions between them. The data support a model in which these factors participate in a regulatory pathway in which Mot1 acts upstream of Spt16.