Competition assay for acyl-coenzyme A incorporation into histone proteins. (a) Schematic diagram of in vitro acylation assay with unlabeled acyl-CoA for substrate competition. In vitro histone acylation assays with nonlabeled acyl-coenzyme A. 14C-labeled coenzyme A incorporation into histone proteins in the presence of an excess amount (5 nmol) of nonlabeled malonyl-coenzyme A (b) and succinyl-coenzyme A (c) was assessed by autoradiography. Acetyl-coenzyme A was used as a control for the substrate specificity. The amounts of added substrate (calf thymus histone proteins) in each reaction were visualized by Coomassie Brilliant Blue (CBB). Molecular weights are indicated on the left side of the figure, and each histone position (histones H3, H2A/B, and H4) is indicated in the right side of the figure.