Histones from Chinese hamster ovary cells. Multiple modified forms: a quantitative approach

A quantitative analysis of histone variants and of their modified forms in exponentially growing Chinese hamster ovary cells is described. A two-step analytical procedure has been developed. Total nuclear proteins were first fractionated on a sodium dodecyl sulfate/polyacrylamide slab gel electrophoresis. After electroelution from the corresponding bands cut out of the gel, each individual histone was analysed on an acetic acid/urea/Triton X-100 slab gel. All the variants and most of the acetylated and phosphorylated molecules were thus resolved. In absence of butyrate, we have detected four, three and two different levels of acetylation respectively for H4, H3, H2A and H2B. Scanning of the stained gel has allowed the determination of the relative amount of each forms. H3 and H4 present a higher turnover of the acetate groups than H2A and H2B. For the four histones, acetate label appeared preferentially in the multi-acetylated forms then gradually in the less acetylated forms. The data suggest that the deacetylation-acetylation process of a given histone molecule involves all the acetate groups of the molecule (three for a triacetylated histone, one for a monoacetylated histone).