Abstract
Chromatin from trout testis at an early stage of development was digested with DNase II (deoxyribonucleate 3''-oligonucleotidohydrolase; EC 3.1.4.6), and the solubilized products were fractionated into Mg2+-soluble and -insoluble components. An examination of the histones from these fractions by 1- and 2-dimensional polyacrylamide gels showed that the highly acetylated species of histone H4 (di-, tri-, and tetra-acetylated) were associated mainly with the Mg2+-soluble material. Digestion of this chromatin fraction with pancreatic RNase converted more than half of it to an insoluble state, and the acetylated H4 remained associated with the precipitated fraction. No changes in the other histones were noted, but 2 other basic proteins were associated with the Mg2+-soluble fraction. Since this fraction is enriched in transcribing gene sequences, it may be that the histone H4 of active genes is present in a highly acetylated state.