Studies on highly metabolically active acetylation and phosphorylation of histones.

The capacity to effectively label tumor cell hostones using very short pulses of [3-H]acetate and [32-P]phosphate (1 to 10 min) has been developed. Four histone fractions F3, F2a1, F2a2, and F2b are extensively acetylated in short time periods. About 70% of the acetate accumulated on the histone during a short pulse is removed with a half-life of similar to 3 min. The rest of the metabolically active acetate is removed with a half-life of 30 to 40 min. Histones F2a1, F2a2, and F1 are acetylated at the NH2 terminus and this modification is metabolically stable. In short pulses, histones are labeled with 32-P in the order F2a2 greater than F1 greater than F3 greater than F2a1 greater than F2b. All fractions have a fairly rapid turnover time (t1/2 similar 20 to 40 min) except F1 phosphate which turns over some 5 times more slowly.