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 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 TATA-binding protein (TBP) from DNA in vitro, but the global relationship between Mot1 and TBP in vivo is unclear. In particular, how Mot1 activates transcription is poorly understood. To address these issues, we 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. 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. Sites of TBP gain are associated with increased gene expression, while decreased TBP binding is associated with reduced gene expression. 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: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:Background: Eukaryotic genes are controlled by proteins that assemble stepwise into a transcription complex. How the individual biochemically-defined assembly steps are coordinated and applied throughout a genome is largely unknown. Here, we model and experimentally test a portion of the assembly process involving the regulation of the TATA binding protein (TBP) throughout the yeast genome. Results: Biochemical knowledge is used to formulate a series of coupled TBP regulatory reactions involving TFIID, SAGA, NC2, Mot1, and promoter DNA. The reactions are then linked to basic segments of the transcription cycle and modeled computationally. A single framework is employed, allowing the contribution of specific steps to vary from gene to gene. Promoter binding and transcriptional output are measured genome-wide using ChIP-chip and expression microarray assays. Mutagenesis is used to test the framework by shutting down specific parts of the network. Conclusion: The model accounts for the regulation of TBP at most transcriptionally active promoters and provides a conceptual tool for interpreting genome-wide data sets. The findings further demonstrate the interconnections of TBP regulation on a genome-wide scale. Keywords: genetic mutation analysis
Project description:An important distinction is frequently made between constitutively expressed housekeeping genes versus regulated genes. Although generally characterized by different DNA elements, chromatin architecture and cofactors, it is not known to what degree promoter classes strictly follow regulatability rules and which molecular mechanisms dictate such differences. We show that SAGA-dominated/TATA-box promoters are more responsive to changes in the amount of activator, even compared to TFIID/TATA-like promoters that depend on the same activator Hsf1. Regulatability is therefore an inherent property of promoter class. Further analyses show that SAGA/TATA-box promoters are more dynamic because TBP recruitment through SAGA is susceptible to removal by Mot1. In addition, the nucleosome configuration upon activator depletion shifts on SAGA/TATA-box promoters and seems less amenable to preinitiation complex formation. The results explain the fundamental difference between housekeeping and regulatable genes, revealing an additional facet of combinatorial control: an activator can elicit a different response dependent on core promoter class.
Project description:An important distinction is frequently made between constitutively expressed housekeeping genes versus regulated genes. Although generally characterized by different DNA elements, chromatin architecture and cofactors, it is not known to what degree promoter classes strictly follow regulatability rules and which molecular mechanisms dictate such differences. We show that SAGA-dominated/TATA-box promoters are more responsive to changes in the amount of activator, even compared to TFIID/TATA-like promoters that depend on the same activator Hsf1. Regulatability is therefore an inherent property of promoter class. Further analyses show that SAGA/TATA-box promoters are more dynamic because TBP recruitment through SAGA is susceptible to removal by Mot1. In addition, the nucleosome configuration upon activator depletion shifts on SAGA/TATA-box promoters and seems less amenable to preinitiation complex formation. The results explain the fundamental difference between housekeeping and regulatable genes, revealing an additional facet of combinatorial control: an activator can elicit a different response dependent on core promoter class.
Project description:An important distinction is frequently made between constitutively expressed housekeeping genes versus regulated genes. Although generally characterized by different DNA elements, chromatin architecture and cofactors, it is not known to what degree promoter classes strictly follow regulatability rules and which molecular mechanisms dictate such differences. We show that SAGA-dominated/TATA-box promoters are more responsive to changes in the amount of activator, even compared to TFIID/TATA-like promoters that depend on the same activator Hsf1. Regulatability is therefore an inherent property of promoter class. Further analyses show that SAGA/TATA-box promoters are more dynamic because TBP recruitment through SAGA is susceptible to removal by Mot1. In addition, the nucleosome configuration upon activator depletion shifts on SAGA/TATA-box promoters and seems less amenable to preinitiation complex formation. The results explain the fundamental difference between housekeeping and regulatable genes, revealing an additional facet of combinatorial control: an activator can elicit a different response dependent on core promoter class.
Project description:An important distinction is frequently made between constitutively expressed housekeeping genes versus regulated genes. Although generally characterized by different DNA elements, chromatin architecture and cofactors, it is not known to what degree promoter classes strictly follow regulatability rules and which molecular mechanisms dictate such differences. We show that SAGA-dominated/TATA-box promoters are more responsive to changes in the amount of activator, even compared to TFIID/TATA-like promoters that depend on the same activator Hsf1. Regulatability is therefore an inherent property of promoter class. Further analyses show that SAGA/TATA-box promoters are more dynamic because TBP recruitment through SAGA is susceptible to removal by Mot1. In addition, the nucleosome configuration upon activator depletion shifts on SAGA/TATA-box promoters and seems less amenable to preinitiation complex formation. The results explain the fundamental difference between housekeeping and regulatable genes, revealing an additional facet of combinatorial control: an activator can elicit a different response dependent on core promoter class.
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.