The nuclear matrix is the site of glucocorticoid receptor complex action in the nucleus

Binding of highly purified glucocorticoid receptor complexes to nuclear matrix was evaluated. Extraction of purified nuclei with 2M potassium chloride and brief deoxyribonuclease digestion leaves a matrix structure containing 1% of nuclear DNA and 6-12% of nuclear proteins. The nuclear matrix retained two binding sites for receptor complexes, a high affinity, low capacity site and a low affinity, high capacity site. These sites have affinities and capacities consistent with those reported for binding of these complexes to intact nuclei. More extensive deoxyribonuclease treatment of the matrix resulted in a marked reduction of high affinity complex binding. Furthermore, the DNA binding form of the receptor complex but not the unactivated receptor complex bound to DNA fibers anchored to nuclear matrix as visualized by 18 nm gold particle receptor complexes. The data suggest that the nuclear matrix is the major site for coordinating glucocorticoid hormone action in the nucleus.