Preferential solubilization of Triton X-100 resistant nuclear glucocorticoid receptors by deoxyribonuclease I

Nuclei, prepared by hypo-osmotic lysis from rat thymocytes that had been incubated at 37 degrees C with 20 nM [1,2,4-3H] triamcinolone acetonide, contained 2600-2800 stably and specifically bound steroid molecules per nucleus, 70-80% of which were retained after treatment with Triton X-100. DNAase I was more effective than DNAase II in solubilizing detergent-resistant glucocorticoid-receptor complexes from nuclei at both 0 degrees C and 37 degrees C; at 0 degrees C, DNAase I digestion released 50-55% of the bound steroid with only 10% digestion of DNA. These results imply that the glucocorticoid-receptor complex is preferentially associated with transcriptionally active chromatin.