BioProject

ISWI-family chromatin remodelers organize nucleosome arrays, while SWI/SNF-family remodelers (RSC) disorganize and eject nucleosomes, implying an antagonism that is largely unexplored in vivo. More...

ISWI-family chromatin remodelers organize nucleosome arrays, while SWI/SNF-family remodelers (RSC) disorganize and eject nucleosomes, implying an antagonism that is largely unexplored in vivo. Here, we describe two independent genetic screens for rsc suppressors that yielded mutations in the promoter-focused ISW1a complex, or mutations in the ‘basic patch’ of histone H4 (an epitope that regulates ISWI activity), strongly supporting RSC-ISW1a antagonism in vivo. RSC and ISW1a largely co-localize, and genomic nucleosome studies using rsc isw1 mutant combinations revealed opposing functions: promoters classified with a nucleosome-deficient region (NDR) gain nucleosome occupancy in rsc mutants, but this gain is attenuated in rsc isw1 double mutants. Furthermore, promoters lacking NDRs have the highest occupancy of both remodelers, consistent with regulation by nucleosome occupancy, and decreased transcription in rsc mutants. Taken together, we provide the first genetic and genomic evidence for RSC-ISW1a antagonism, and reveal different mechanisms at two different promoter architectures. Overall design: Genome-wide nucleosome occupancy maps in wild-type, mutant RSC, and mutant ISW1 strains were generated by hybridization of mononucleosomal DNA to microarrays. Strains carrying Sth1 degron and either pGal-UBR1 (YBC2191) or ubr1 null (YBC2192) represent RSC null and RSC wildtype, respectively. Strains carrying Sth1 degron isw1 null and either pGal-UBR1 (YBC2467) or ubr1 null (YBC2468) represent RSC null isw1 null and RSC wildtype isw1 null, respectively. Mononucleosomes were isolated from three independent biological replicates from each genotype. Please note that each sample consists of three replicates (i.e. three raw data files) and the sample data table contains combined quantile normalized data of the replicates. Less...