IDENTIFICATION OF A GENE ENCODING A YEAST HISTONE H4 ACETYLTRANSFERASE

A collection of yeast temperature-sensitive mutants was screened by an enzymatic assay to find a mutant defective in the acetylation of histone H4. The assay used a fractionated cell extract and measured acetylation of a peptide corresponding to amino acids 1-28 of H4. There are at least two activities in this fraction that acetylate the peptide. A mutation, hat1-1, that eliminates one of the activities was identified and mapped to a locus near the centromere of chromosome XVI. The HAT1 gene was cloned and found to encode a protein of 374 amino acids. Analysis of the peptide used in the assay demonstrated that the HAT1 enzyme acetylates lysine 12 of histone H4. hat1 mutants have no obvious growth defects or phenotypes other than the enzyme defect itself. The HAT1 protein expressed in Escherichia coli gave histone acetyltransferase activity in vitro, demonstrating that HAT1 is the structural gene for the enzyme.