GSE20078
The effect of bound RSC/nucleosome complex on chromatin architecture and gene expression at the GAL genes of yeast
How is chromatin architecture established and what role does it play in activation of transcription?  We show that a regulatory locus in yeast (the UASg) bears, in addition to binding sites for the activator Gal4, sites bound by the protein RSC.  RSC tightly positions a nucleosome, evidently partially unwound, in a structure that facilitates Gal4 binding to its sites.  The complex comprises a barrier that suffices to impose characteristic features of chromatin architecture.  Removal of RSC allows ordinary nucleosomes to form more broadly over the UASg, and these nucleosomes compete with (but do not exclude) Gal4 binding to its sites.  Taken with our previous work, the results show that both prior to and following induction specific DNA binding proteins are the predominant determinants of chromatin architecture at the GAL1/10 genes. RSC/nucleosome complexes are found scattered throughout the yeast genome.  We surmise, also, that Gal4 works in higher eukaryotes despite whatever obstacle broadly positioned nucleosomes present. Overall design: Chromatin was digested under conditions that yielded primarily mononucleosomes, and RSC-bearing fragments were recovered on IgG-beads.  Fragments (of size ca. 50-200 bp) were analyzed by paired-end high throughput DNA sequencing (Illumina).  This technique determines the sequences found at both ends of each fragment, thus revealing the sizes and genomic origin of these fragments.