Acetylation and calcium-dependent phosphorylation of histone H3 in nuclei from butyrate-treated HeLa cells.

In HeLa nuclei, 1 microM Ca2+ stimulates 3-fold the phosphorylation of histone H3. Prior treatment of cells with Na butyrate increases the degree of H3 phosphorylation and reveals a correlation between the extents of H3 acetylation and phosphorylation. Acetylation of H3 increases its accessibility to the calcium-dependent kinase. Phosphorylation of H3 occurs at a serine residue located in the trypsin-sensitive region of the protein. Brief digestion of nuclei with DNase I preferentially releases the phosphorylated form of H3 from chromatin.