Steroid receptor activation: the glucocorticoid receptor as a model system

The glucocorticoid receptor has been used as a model for steroid receptor activation. Because of recent evidence for the essentially nuclear location of the unoccupied receptors of 1,25-dihydroxycholecalciferol and 17 beta-estradiol, the significance of the activation mechanism converting unactivated receptor complexes to DNA-binding forms is unclear for some receptors. Up to now the weight of evidence favors a cytoplasmic location of the unactivated glucocorticoid receptor. In this article we describe studies on the nature of the activation mechanism and of regulatory factors.