Dynamics of histone acetylation in Saccharomyces cerevisiae

Rates of turnover for the posttranslational acetylation of core histones we re measured in logarithmically growing yeast cells by radioactive acetate l abeling to near steady-state conditions. On average, acetylation half-lives were approximately 15 min for histone H4, 10 min for histone H3, 4 min for histone H2B, and 5 min for histone H2A. These rates were much faster than the several hours that have previously been reported for the rate of genera l histone acetylation and deacetylation in yeast. The current estimates are in line with changes in histone acetylation detected directly at specific chromatin locations and the speed of changes in gene expression that can be observed. These results emphasize that histone acetylation within chromati n is subject to constant flux. Detailed analysis revealed that the turnover rates for acetylation of histone H3 are the same from mono- through penta- acetylated forms. A large fraction of acetylated histone H3, including poss ibly all tetra- and penta-acetylated forms, appears subject to acetylation turnover. In contrast, the rate of acetylation turnover for mono- and di-ac etylated forms of histones H4 and H2B, and the fraction subject to acetylat ion turnover, was lower than for multi-acetylated forms of these histones. This difference may reflect the difference in location of these histones wi thin the nucleosome, a difference in the spectrum of histone-specific acety lating and deacetylating enzymes, and a difference in the role of acetylati on in different histones.