Acetylation of histones during spermatogenesis in the rat

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Acetate was actively incorporated into rat testis histones when testis cells were prepared by the trypsinization technique in the presence of [ 3H]acetate. The acetylation was enhanced by 10 m m sodium butyrate. Although histones H3 and H4 were the only histones which incorporated high levels of acetate, the testis-specific histones TH2B and TH3 also appeared to incorporate acetate. This was shown by electrophoresis of the histones on polyacrylamide gels containing Triton X-100. Results, obtained from analysis of histones by two-dimensional gel electrophoresis, confirmed a recent report (P. K. Trostle-Weige, M. L. Meistrich, W. A. Brock, K. Nishioka, and J. W. Bremer, (1982) J. Biol. Chem. 257, 5560–5567) that TH2A was a testis-specific histone. The results also confirmed the H2A nature of a testis-enriched histone band, previously designated X2. When histones from populations of cells enriched in specific testis cell types, representing various stages of spermatogenesis, were examined, the patterns of acetylation varied dramatically. Very high levels of acetate were incorporated into multiacetylated species of histone H4 from a population of cells enriched in transition stage spermatids (steps 9–12) compared to the levels of acetate incorporated into H4 from round spermatids (steps 1–8) and earlier stages of spermatogenesis, where acetate was incorporated primarily into the monoacetylated species of H4. Thus, a striking correlation exists between the time of hyperacetylation of histone H4 and the time of removal of histones for their replacement by the basic spermatidal transition proteins designated TP, TP2, and TP4. Hyperacetylation of histone H4 may facilitate the removal of the entire histone complement during the protein transition. In any case, it must be an obligatory step in the dramatic process.