Testicular cytosol factors inhibit the binding of steroid-receptor complexes to chromatin

Abstract

Testicular and prostatic androgen-receptor complexes as well as uterine estradiol-receptor complexes, partially purified by ammonium sulfate precipitation (15–37%), were bound to germ cell chromatin. At equivalent concentrations, less testicular androgen-receptor complexes bound to chromatin than did the other two steroid-receptor complexes. Addition of a partially purified testicular androgen-receptor preparation with prostatic androgen-reeeptor or uterine estradiol-receptor preparation to the binding interaction mixture reduced the binding of either of the latter two steroid-receptor complexes to chromatin. These data suggest the presence of inhibitory factor(s) in the testicular receptor preparations. Testicular cytosols were fractionated by ammonium sulfate precipitation into fractions A (15–37% saturation), B (37–50%) and C (50–75%). All fractions inhibit binding of these steroid-receptor complexes to chromatin. Fractions A and B appear to be heat labile, while fraction C was more stable. Further fractionation of A and C fractions on DEAE cellulose yielded A 1 and C 1 (filtrates) as well as A 2 and C 2 (0.3 M Nacl eluents), respectively. Subfractions A 1, A 2, and C 1 contained inhibitory factors for the binding of steroid-receptor complexes to chromatin while C 1 showed no effect. These data demonstrated that testicular cytosol contains a variety of inhibitory factors which affect the binding of both androgen-receptor and estradiol-receptor complexes to chromatin.