INTERACTION OF STEROID HORMONES WITH HISTONES IN VITRO

1. [3H]Hydrocortisone is bound more to F3 histone than to F1 or F2a histone in vitro. Aggregated F2a histone binds more [3H]hydrocortisone than does unaggregated F2a histone. 2. The binding of [3H]hydrocortisone to arginine-rich histone increases with the time of incubation. There is a linear increase of binding with increasing steroid concentration. The binding per mg histone decreases with increasing histone concentration. 3. Histone-bound [3H]hydrocortisone is less easily removed from aqueous solution by extraction with chloroform, than is free [3H]hydrocortisone. 4. When the histone-[3H]hydrocortisone complex is added to a DNA solution, a large amount of steroid co-precipitates with the DNA-histone. 5. Evidence is presented to suggest that the hydrophobic region on the arginine-rich histone molecule has a relatively larger [3H]hydrocortisone-binding capacity than the remainder of the molecule. 6. Arginine-rich histone which was oxidized with performic acid bound more [3H]hydrocortisone than did untreated histone. 7. A model for the structure of arginine-rich histone and a possible mode of interaction of the arginine-rich histone with DNA, is tentatively proposed. © 1969.