Mechanisms of ACTH(cAMP)-dependent transcription of adrenal steroid hydroxylases

The action of peptide hormones from the anterior pituitary regulates transcription of a large number of genes located in most, if not all, tissues. This action is mediated through regulation of steroid hormone production in the steroidogenic factories (adrenals, gonads). These steroid hormones are transported through the circulation to the peripheral tissues where they serve as ligands for the family of zinc-finger nuclear receptor transcription factors. The mechanisms by which peptide hormones regulate steroid hormone production include a chronic response mediated by elevated levels of cAMP resulting from the binding of peptide hormones to their cell surface receptors which enhances transcription of the genes encoding steroid hydroxylases required for steroid hormone biosynthesis. The action of ACTH in the adrenal cortex has been 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 expression 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 each steroid hydroxylase gene requires a different transcription factor.