The Polynucleotide Binding Sites of Estradiol Receptor Complexes

Summary

As a model for interaction of steroid receptors with DNA, the binding of estradiol receptor complexes (E₂R) to oligodeoxynucleotides, covalently linked to cellulose, was studied in detail. Binding was optimal at concentrations of monovalent cationic salts at, or near, isotonic levels and was selective for intracellular receptors in contrast to extracellular steroid binding proteins. Among the oligomers, the order of affinity was oligo dG> oligo dT≥ oligo dC≫oligo dA≫oligo dI. The binding to oligo dG was stable to 37° C exposure and the processes of adsorption and desorption, while reactivity with oligo dT, oligo dC and oligo dA was labile. The decrease in binding following purification was restored by histone 2B. Oligo dG binding was the most resistant to inhibition by cibacron blue F3GA (CB) and pyridoxal-5-phosphate. On the basis of these data, a hypothesis is proposed for the interaction of mouse uterine cytosol E₂R with prevalent nonspecific and putative specific sequences of DNA.