MUTATIONS IN CHROMATIN COMPONENTS SUPPRESS A DEFECT OF GCN5 PROTEIN IN SACCHAROMYCES-CEREVISIAE

The yeast GCN5 gene encodes the catalytic subunit of a nuclear histone acetyltransferase and is part of a high-molecular-weight complex invo lved in transcriptional regulation, In this paper we show that full ac tivation of the HO promoter in vivo requires the Gcn5 protein and that defects in this protein can be suppressed by deletion of the RPD3 gen e, which encodes a histone deacetylase. These results suggest an inter play between acetylation and deacetylation of histones in the regulati on of the HO gene, We also show that mutations in either the H4 or the H3 histone gene, as well as mutations in the SIN1 gene, which encodes an HMG1-like protein, strongly suppress the defects produced by the g cn5 mutant, These results suggest a hierarchy of action in the process of chromatin remodeling.