Transcriptional regulation of the genes encoding the cytochrome P-450 steroid hydroxylases

This chapter discusses the transcriptional regulation of the genes encoding the cytochrome P-450 steroid hydroxylases. Steroid hormones are essential regulators of such diverse processes as accommodation to stress, carbohydrate metabolism, fluid and electrolyte balance, and reproduction. All endogenous steroids are derived from cholesterol and, therefore, have the cyclopentanoperhydrophenanthrene nucleus as a part of their basic structure. Modifications to this basic nucleus generate specific ligands for the members of the nuclear receptor family of transcription factors, accounting for their specific actions in different target tissues. Pregnenolone and 17α-hydroxypregnenolone are converted into progesterone and 17α-hydroxyprogesterone, respectively, by the microsoma1 enzyme 3β-hydroxysteroid dehydrogenase, which is one of the few noncytochrome P-450 steroid-biosynthetic enzymes and essential for the production of all major physiological steroid hormones. The expression of these functionally distinct CYP11B genes in the appropriate cortical zones plays an essential role in the gland's ability to separately regulate the biosynthesis of mineralocorticoids and glucocorticoids. © 1995 Academic Press Inc.