MECHANISMS OF ACTH(CAMP)-DEPENDENT TRANSCRIPTION OF ADRENAL-STEROID HYDROXYLASES

The action of peptide hormones from the anterior pituitary regulates t ranscription of a large number of genes located in most, if not all, t issues. This action is mediated through regulation of steroid hormone production in the steroidogenic factories (adrenals, gonads). These st eroid hormones are transported through the circulation to the peripher al tissues where they serve as ligands for the family of zinc-finger n uclear receptor transcription factors. The mechanisms by which peptide hormones regulate steroid hormone production include a chronic respon se mediated by elevated levels of cAMP resulting from the binding of p eptide hormones to their cell surface receptors which enhances transcr iption of the genes encoding steroid hydroxylases required for steroid hormone biosynthesis. The action of ACTH in the adrenal cortex has be en studied in greatest detail leading to identification of unique cAMP -response sequences (CRS) in the different bovine steroid hydroxylase genes. Most likely FSH and LH mediate steroid hydroxylase gene express ion in the gonads via the same response elements. Unlike developmental /tissue-specific transcription of these genes which is regulated by a common transcription factor (SF-1), cAMP-dependent transcription of ea ch steroid hydroxylase gene requires a different transcription factor.