Immobilized oligodeoxynucleotides as probes of the DNA-binding sites of mouse steroid holoreceptors

Abstract

Steroid hormone receptors are DNA-binding proteins with distinct domains for the steroid ligand and for polydeoxyribonucleotides. The characteristics of the polynucleotide-binding sites of the mouse liver dexamethasone receptor, kidney testosterone and estradiol receptors, and uterine estradiol receptor were examined by using oligodeoxynucleotides covalently linked to cellulose as probes. Only dexamethasone receptor binding to oligodeoxynucleotides was dependent upon activation by increased salt concentrations or temperature. The dexamethasone and estradiol receptors required a distinct concentration of KCl for maximal binding to oligodeoxynucleotide-cellulose. In contrast, binding of mouse kidney testosterone receptor was not stimulated by KCl although it was decreased at 0.2 M KCl. The nucleotide affinities of the mouse receptors generally followed the order of binding to oligo(dG)- greater than oligo(dT)- greater than oligo(dC)- greater than oligo(dA)-cellulose. However, the liver dexamethasone receptor bound to oligo(dT)- more avidly than to oligo(dC)-cellulose, while neither the testosterone nor the estradiol receptors clearly differentiated between the oligodeoxypyrimidine celluloses. Although the binding of the kidney testosterone receptor was poorest of those studied, it bound to oligo(dA)-cellulose relatively more efficiently than did the other steroid receptors. Thus, differences were revealed in the requirements for activation, added salt for binding, and relative binding efficiencies to the ligands among different steroid receptors from the same tissue and among the same steroid receptors from different tissues.