Studies on nuclear proteins II. Quantitative distribution of histone fractions in various tissues

Abstract

1. 1. A method for quantitative evaluation of starch-gel electrophoretograms of histones from various tissues was elaborated. Small amounts of AlCl 3 (0.2–0.6 mM) were found to improve the electrophoretic separation of histone fractions and substantially decrease the trailing of the fractions. 2. 2. The contents of the five main electrophoretic bands were determined for calf thymus, rat spleen, rat liver, regenerating rat liver and for Novikoff hepatoma histones. Isolated calf-thymus histone fractions (F1, F2a, F2b, and F3) were used for standard determinations. 3. 3. Various tissues were found to contain different amounts of the five main histone fractions as resolved by teh starch-gel electrophoresis. The very lysine-rich Fraction F1 and the moderately lysine-rich Fraction 2a 11 varied very little in the analyzed tissues. The amount of electrophoretically fast FRaction 2a 1 decreased with the increasing rate of cell division, e.g. in regenerating rat liver or Novikoff hepatoma. The moderately lysine-rich histones F2b showed the greatest variability in the F2 group. Whereas in calf thymus and in rat liver the contents of this fraction were approximately equal, regeneration increased and neoplasia decreased the amount of this histone. The arginine-rich Fraction 3 was found to be substantially increased in the Novikoff hepatoma. It was proposed that if histones function as genetic suppressors, the mechanism regulating histone biosynthesis could serve to control the cellular differentiation.