STRUCTURAL-CHANGES OF SOLUBLE RAT-LIVER CHROMATIN INDUCED BY THE SHIFT IN PH FROM 7 TO 9

  • 1 January 1981
    • journal article
    • research article
    • Vol. 25  (1) , 19-27
Abstract
Soluble rat liver chromatin was studied at pH 7 and at pH 9. In order to remove selectively non-histone components or non-histone components and histone H1, fractionation of chromatin was performed at pH 7 and pH 9 at different ionic strengths. The salt-dependent condensation of the fractionated chromatin was analyzed in the EM. There is no difference between the appearance of H1-depleted chromatin at pH 7 and pH 9. In H1-containing chromatin the shift from pH 7-pH 9 leads to the following morphological changes. At very low ionic strength the nucleosomes unravel partially or totally and the zigzag-shaped fibers disappear in favor of beads-on-a-string. With increasing ionic strength the filaments condense into fibers; these fibers appear distorted and clearly less ordered than at pH 7. There is no indication of a release or displacement of histone H1. The pH effect is completely reversible. A pH-induced change in the mode of action of histone H1 is suggested in the formation of nucleosome beads and higher order chromatin structures.