Project description:Chromatin remodelers are essential for the maintenance of chromatin structure and gene regulation. In this study, we examined the role of histone acetyltransferases Gcn5 and Esa1 in regulating RSC and histone occupancies and transcription genome-wide. We identify the contrasting roles of HATs in modulating RSC occupancies in promoters and ORFs. In HAT mutants, we found RSC occupancies unexpectedly accumulate in the NDRs harboring the “fragile nucleosomes (FNs)” than those with the stable -1 nucleosomes. Moreover, the accumulation was more significant in the H4 HAT Esa1 mutant than in the Gcn5 mutant. However, NDR accumulation was not observed in the cells lacking the H3 or H4 tails, suggesting that unacetylated/hypoacetylated tails are critical for the increased RSC observed in the mutants. Furthermore, we observe marked increases in histone occupancies in NDRs in the mutants genome-wide. An increase in both RSC and histones at NDRs in the HAT mutants suggests that FNs use hypoacetylated tails to recruit RSC to NDRs, and acetylation is needed for efficient histone eviction. Thus, our data implicate HATs, in addition to RSC, in maintaining NDRs. Increased histone and RSC occupancies in promoters and reduced RSC occupancies in ORFs in the HAT mutants reduce TBP and Pol II binding at promoters.
Project description:Genome-wide cooperation by HAT Gcn5, remodeler SWI/SNF, and chaperone Ydj1 in promoter nucleosome eviction and transcriptional activation
Project description:We have investigated the genome-wide occupancy of Sas3p by ChIP-Chip, using tiled microarrays. Using this technique, it has been described that H3K14 and H3K9 acetylation is enriched at promoter regions and transcriptional start sites of active genes. Considering that Sas3p is a HAT whose main target in vitro is H3K14 we expected to detect Sas3 binding largely to promoter regions of genes. Surprisingly, we found that Sas3p is associated to the coding regions of genes, with a peak enrichment located) within the 5’ half of the ORF, and this enrichment drops substantially toward the 3’ region of the ORF. This result is very similar to that obtained for Yng1 genome-wide occupancy, also a component of the NuA3 complex, suggesting that this complex could be involved in transcriptional elongation, at least, in an initial step of the process.
