Modulation of the Nucleosome Structure by Histone Acetylation

Abstract

A rapid procedure for the isolation of core particles from Chinese hamster ovary cells is described which permits measurements, usually at the day of their preparation. Particles of 145 .+-. 5 base pairs, derived from interphase cells, will be compared with the analog specimens from butyrate-treated cells, metaphase cells and a standard preparation from chicken erythrocytes. Butyrate causes an increase in the acetylation of histones H3 and H4, which induces alterations of the interhistone and histone-DNA interactions. Changes in the interhistone contacts, correlated to an extension of .alpha.-helical segments, lead to an altered accessibility of the H3 cysteine side-chains and to a different histone displacement by protamines. Histone-DNA contacts are loosened in parts and this is particularly evident from the changes in the premelting region of a thermal denaturation profile.