COMPARISON OF CAMP-RESPONSIVE DNA-SEQUENCES AND THEIR BINDING-PROTEINS ASSOCIATED WITH EXPRESSION OF THE BOVINE CYP17-GENES AND CYP11A-GENES AND HUMAN CYP21B-GENES

Maintenance of optimal steroidogenic capacity in the adrenal cortex requires the action of the peptide hormone ACTH. Upon binding to its cell surface receptor ACTH activates adenylate cyclase leading to elevated levels of intracellular cAMP which in turn enhances transcription of the genes encoding the enzymes involved in the conversion of cholesterol to the steroid hormones. By deletion analysis of their upstream regions, the genes encoding the steroid hydroxylases P450c17, P450c21 and P450scc (CYP17, CYP21B and CYP11A, respectively) were found to contain unique cAMP-responsive sequences (CRSs). These sequences are unique in the sense that they have not previously been described to be associated with other genes whose transcription is regulated by cAMP. Furthermore they appear to bind unique nuclear proteins or transcription factors not previously associated with cAMP-dependent transcription. This review summarizes the relatedness of these CRSs in the bovine CYP17 and CYP11A genes and the human CYP21B gene and provides an up-to-date summary of the properties of their nuclear DNA-binding proteins.