Regulation of cytochrome P-45011 beta gene expression by adrenocorticotropin

Abstract

Recombinant DNA clones corresponding to 11 beta-hydroxylase cytochrome P-450 (P-450(11)beta) have been identified in a bovine adrenocortical cDNA library. These clones, pB11 beta-1 and pB11 beta-2, hybridize to at least three RNA species, 7.2, 6.2, and 4.3 kilobases in length, present in the adrenal cortex. All three RNA species directed cytochrome P-450(11)beta synthesis in an in vitro translation system. Expression of the cytochrome P-450(11)beta gene is tissue specific in that these transcripts were not detected in liver, heart, kidney, or corpus luteum. In cultured bovine adrenocortical cells, adrenocorticotropin (ACTH) or dibutyryl cAMP increased the concentration of cytochrome P-450(11)beta transcripts. This increase appears to be at least partially due to de novo transcription as shown by the action of actinomycin D which effectively blocked the ACTH-induced increase in cytochrome P-450(11)beta RNA level. Furthermore, cycloheximide administered prior to or along with ACTH resulted in the blockage of any new transcription of the cytochrome P-450(11)beta gene as evidenced from the level of RNA. Thus, in addition to potential effects on RNA stabilization, a primary action of ACTH in the regulation of the level of cytochrome P-450(11)beta may be to mediate the induction of an unidentified adrenocortical protein which is required for the activation of cytochrome P-450(11)beta gene expression. These results, together with previous studies (Kramer, R.E., Rainey, W.E., Funkenstein, B., Dee, A., Simpson, E. R., and Waterman, M. R. (1984) J. Biol. Chem. 259, 707-713) that showed increased intracellular levels of cAMP upon treatment of bovine adrenocortical cell cultures with ACTH, suggest a role for cAMP-mediated events in the regulation of cytochrome P-450(11)beta gene expression.