GCN5P IS INVOLVED IN THE ACETYLATION OF HISTONE H3 IN NUCLEOSOMES

Enzymatic extracts from a gcn5 mutant and wild-type strains of Sacchar omyces cerevisiae were chromatographically fractionated and the histon e acetyltransferase activities compared. When free histones were used as substrate, extracts from wild-type cells showed two peaks of activi ty on histone H3 but extracts from gcn5 mutant cells showed only one. With nucleosomes as substrate, the histone acetyltransferase activitie s present in extracts from the gcn5 mutant strain were not able to mod ify H3 whereas wild-type cell extracts acetylated intensely this histo ne. The activity that acetylated nucleosome-bound H3 behaved as a 170- kDa complex. We suggest that Gcn5p represents a catalytic subunit with in a multiprotein complex containing proteins that confer on it the ab ility to acetylate H3 in nucleosomes. (C) 1997 Federation of European Biochemical Societies.