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: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: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
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