Transcriptional repression of the yeast CHA1 gene requires the chromatin-remodeling complex RSC

eukaryotes, DNA is packaged into chromatin, a compact structure that must b e disrupted when genes are transcribed by RNA polymerase II. For transcript ion to take place, chromatin is remodeled via nucleosome disruption or disp lacement, a fundamental transcriptional regulatory mechanism in eukaryotic organisms. Here we show that the yeast chromatin-remodeling complex, RSC (r emodels the structure of chromatin), isolated on the basis of homology to t he SWI/SNF complex, is required for proper transcriptional regulation and n ucleosome positioning in the highly inducible CHA1 promoter. In the absence of Sth1p/Nps1p (a homolog of Swi2p/Snf2p) or of Swh3p (a homolog of Swi3p) , expression of CHA1 in non-induced cells is increased to a level comparabl e with that of fully induced cells. Furthermore, in non-induced cells deple ted for Sth1p/Nps1p or Swh3p, a nucleosome positioned over the TATA box of the CHA1 promoter is disrupted, an architectural change normally only obser ved during transcriptional induction. In addition, deletion of the gene-spe cific activator Cha4p did not affect derepression of CHA1 in cells depleted for Swh3p. Thus, CHA1 constitutes a target for the RSC complex, and we pro pose that RSC is essential for maintaining a repressive chromatin structure at the CHA1 promoter.