The Effects of Ribonuclease on Rat Liver Dexamethasone Receptor: Increased Affinity for Deoxyribonucleic Acid and Altered Sedimentation Profile*

Abstract

The ability of the dexamethasone (9α-fluoro-11β, 17,21-trihydroxy-16α-methylpregna-1,4-diene-3,20-dione)-receptor complex to bind to DNA-cellulose is stimulated by RNase treatment of the activated receptor. Both RNase A and RNase T₁ can induce the stimulation. The enhancement of the DNA binding ability occurs concomitantly with an alteration of the sedimentation profile of the dexamethasone-receptor complex from the 7–8S form to the 3–4S form in low salt sucrose gradients. If RNase treatment occurs in the presence of sodium molybdate, both the increase in DNA binding ability and the alteration in sedimentation profile fail to occur. Treatment of the receptor with high salt suggests that the 3–4S form can reversibly combine with a factor in a salt-sensitive association. These experiments indicate that the 7–8S form of the dexamethasone-receptor complex is associated with a RNA molecule(s) that can be removed by RNase treatment or salt dissociation, and that this RNA inhibits the binding of the receptor to DNA.