Proteinase associated with chromatin isolated from liver and hepatoma of rat is stimulated by salt, and, of the histone fractions, lysine-rich (F1) histone is preferentially degraded by this enzyme at an ionic strength comparable with that found in the nucleus. However, there appears to be no strict relationship between the activity of the proteinase and growth rates of hepatomas. Chromatin isolated from a fast-growing tumour, Ehrlich ascites carcinoma, shows no apparent proteinase activity in the presence of salt.
