Steady-state levels of histone acetylation in Saccharomyces cerevisiae.
Waterborg, JH
J. Biol. Chem. 2000 April 28; 275(17): 13007-13011
The importance of control of the levels of histone acetylation for the control of gene expression in eukaryotic chromatin is being elucidated, and the yeast Saccharomyces cerevisiae has proven to be an important model system. The level of histone acetylation in yeast is the highest known. However, only acetylation of H4 has been quantified, and reports reveal loss of acetylation in histone preparations. A chaotropic guanidine-based method for histone isolation from intact wild-type cells or from a single-step nuclear preparation with butyrate preserves acetylation of all core histones. Histone H4 has an average of more than 2 acetylated lysines per molecule, distributed over 4 sites. Histones H2A, H3, and H2B have 0.2, approximately 2, and >2 acetylated lysines per molecule, respectively, distributed across 2, 5, and 6 sites. Thus, yeast nucleosomes carry, on average, 13 acetylated lysines per octamer, i. e. just above the threshold of 10-12 deduced for transcriptionally activated chromatin of animals, plants, and algae. Following M(r) 100,000 ultrafiltration in 2.5% acetic acid, yeast histone H3 was purified to homogeneity by reversed-phase high pressure liquid chromatography. Other core histones were obtained at 80-95% purity.
Dynamics of Histone Acetylation in Saccharomyces cerevisiae.
Waterborg, JH
Biochemistry 2001 January 25; 40: 2599-2605
Rates of turnover for the posttranslational acetylation of core histones were measured in
logarithmically growing yeast cells by radioactive acetate labeling 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 general 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 chromatin 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 possibly all tetra- and penta-acetylated forms, appears subject
to acetylation turnover. In contrast, the rate of acetylation turnover for mono- and di-acetylated forms of
histones H4 and H2B, and the fraction subject to acetylation turnover, was lower than for multi-acetylated
forms of these histones. This difference may reflect the difference in location of these histones within the
nucleosome, a difference in the spectrum of histone-specific acetylating and deacetylating enzymes, and
a difference in the role of acetylation in different histones.