Chicken erythrocyteβ-globin chromatin: enhanced solubility is a direct consequence of induced histone hyperacetylation

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Abstract
Chicken immature red blood cells were incubated for 1 hour in Swim's medium containing 3H-acetate and 10mM n-butyrate. During the incubation period, the small percentage of dynamically acetylated and deacetylated histone is radiolabeled and hyperacetylated. A second effect of the n-butyrate incubation is to shift a small subset of nucleohistone into a soluble form. This chromatin is predominantly polynucleosome size (approximately dimer to pentamer) and can be separated from soluble mononucleosomes by 5–30% sucrose density gradient centrifugation. The soluble polynucleosomes are 25–30 fold enriched for adult β-globin (βA) DNA and contain the hyperacetylated histones. We have tested whether histone hyperacetylation is responsible for the enhanced β-globin chromatin solubility by in vitro deacetylation of the soluble chromatin histones. This procedure converts the β-globin polynucleosomes to an insoluble form, demonstrating that histone hyperacetylation is in fact directly responsible for the increased solubility of the βA chromatin.