Interaction of histones in glucocorticoid receptor binding to DNA in vitro.

We recently demonstrated that [1,2,4-3H]triamcinolone acetonide-receptor complexes purified 3000-fold from rat livers bound strongly to histone-agarose. The binding was not electrostatic, because it was not affected by ionic strength. In this in vitro study, we examined the effects of histones on the binding of glucocorticoid-receptor complexes to DNA-cellulose. The binding of the purified [1,2,4-3H]triamcinolone acetonide-receptor complexes to calf thymus DNA-cellulose was increased markedly in a dose-dependent manner by low concentrations of a whole histone mixture (H2A, H2B, H3, H4, and H1 from calf thymus), but this high level of binding decreased at higher concentrations of the histone mixture. The binding of receptor complexes to DNA-cellulose was enhanced greatly by histones H4 and H3 and slightly by histone H2A, was not affected by histone H2B, and was inhibited by histone H1. Similar stimulatory and inhibitory effects of these histones were seen when the DNA-cellulose was preincubated with the various histones and then washed to remove free histones before measurement of binding of the receptor complex. These results suggest that histones are involved in the mechanism of action of glucocorticoid hormones.