Histone H4 acetylation in human cells. Frequency of acetylation at different sites defined by immunolabeling with site-specific antibodies.

Histone H4 can be reversibly acetylated at lysine residues 5, 8, 12 and 16. It is possible that acetylation of individual residues will exert specific effects on chromatin function, but this hypothesis is difficult to test with present techniques for analysis of acetylation. To address this problem, we have prepared antibodies which distinguish H4 molecules acetylated at each of the sites used in vivo. By electrophoresis and immunolabeling we have shown that, in H4 from human cells, the four lysine residues are acetylated in a preferred, but not exclusive order, namely lysine 16, followed by 12 and 8, followed by 5.