Sites of in Vivo Acetylation in Trout Testis Histone IV

During the process of spermatogenesis in rainbow trout, there is extensive acetylation of some histone fractions. A large proportion of the acetyl groups is present in histone IV, and the sites of acetylation in this fraction have been determined. Four lysyl residues in the NH2-terminal region at positions 5, 8, 12, and 16 were found to be acetylated in a fraction of the histone IV molecules. Acetylation of each of these 4 lysyl residues can probably occur independently of the others, at least to some extent. This leads to a complex mixture of modified histone IV molecules, which is partially reflected in the starch gel pattern of this protein. There seems to be no acetylation of the other lysyl residues in the molecule.