1. 1. Selective extraction of the very lysine-rich histone fraction F1 does not increase the activity of chromatin as a template for RNA synthesis in vitro. Removal of either arginine-rich histones F2a and F3 or lysine-rich histones F2b (together with F1) results in an increase of the template activity of chromatin. 2. 2. (NH4)2SO4 removes selectively the lysine-rich histone fractions F1 and F2b. Even in 1.0 M (NH4)2SO4 the arginine-rich histones F2a and F3 remain associated with chromatin. 3. 3. (NH4)2SO4 in 0.2 M concentration (as does 0.5 M NaCl) dissociates only the F1 histone fractions without simultaneous increase of the DNA-dependent RNA synthesis. Since similar concentrations of (NH4)2SO4 increase the in vitro nuclear RNA synthesis several-fold, it can be concluded that the salt activation of RNA synthesis in isolated nuclei or chromatin is caused by the activation of RNA synthesis system and not by template derepression of chromatin. 4. 4. The pH of the salt solutions used to extract histones influences the solubility of nonhistone proteins. At pH 6.0 little nonhistone protein is extracted while at pH 8.0 considerable amount of nonhistone proteins is released into the solution.
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