TRANSCRIPTIONAL REGULATION OF THE ADRENAL STEROIDOGENIC ENZYMES

Corticosteroid biosynthesis requires the concerted action of a related group of cytochrome P450 steroid hydroxylases. The genes encoding these steroid hydroxylases exhibit two distinct levels of transcriptional regulation: selective expression in steroidogenic cells and induction in response to trophic hormones. With respect to cell-selective expression, recent studies have identified a nuclear receptor protein expressed only in steroidogenic cells that is postulated to regulate the expression of all cytochrome P450 steroid hydroxylases through common promoter elements. In contrast, the coordinate responses of these genes to trophic hormones are not readily explained by a unifying mechanism, and their hormone responsive expression probably involves multiple promoter elements.