Regulatory mechanisms of cAMP‐dependent and cell‐specific expression of human steroidogenic cytochrome P450scc (CYP11A1) gene

Abstract

Cytochrome P450scc (CYP11 A l ) is the enzyme that catalyzes the side-chain cleavage reaction of cholesterol, the first and rate-limiting reaction in the biosynthesis of steroid hormones in the adrenal cortex. DNase-I-footprinting analysis using nuclear extracts from the bovine adrenal cortex and the 5' upstream regulatory region (nucleotides -1697 to -1523) of the CYPllAl gene, which is mainly required for response to CAMP [Inoue, H., Watanabe, N., Higashi, Y. & Fujii-Kuriyama, Y. (1991) Eur: J. Biochem. 195,, revealed that some protein factors bound to that region.One of the sequences protected by the binding factors is a CAMP-responsive-element (CRE)-like sequence, which is known to be recognized by CRE-binding protein (CREB) or its related proteins, and another is a sequence designated Ad4 which is bound by a tissue-specific factor, Ad4-binding protein (Ad4BP). The region containing the two closely arranged DNA sequences showed a high level of CAMP responsive and cell-specific expression when it was fused to the basal promoters. Introduction of point mutations in these sequences demonstrated that the CREB/ATF factors and Ad4BP bound to the sequences showed synergistic enhancer effects on CAMP-responsive and cellspecific expression of the CYPllAl gene.Expression of cytochrome P450,,, (CYP11 A l ) that catalyzes the first and the rate-limiting reaction in the steroidogenic pathway from cholesterol, is regulated by adrenocorticotropin via CAMP as an intracellular mediator [ 11. The regulatory mechanisms of transcription of the steroidogenic P450 genes are believed to be different from those involving CAMP-response-element (CRE) and CRE-binding protein (CREB) or its related factors in the genes that show CAMPinducible transcription [2 -9, 351 because no typical CRE sequence was found in the regulatory regions examined, except for the steroid lip-hydroxylase gene (CYPIIBI) promoter [lo,28, 291. Recently, human CYP17 and CYP21A2 genes have been demonstrated to be controlled by CREB or its related factors through binding to the DNA elements 111, 121, although they do not have a typical CRE consensus sequence. Regulatory mechanisms of CYPllAl expression have been investigated with mouse, rat, bovine, sheep and human genes [13][14][15][16][17][18] 331. In the bovine CYPllA gene [15, 181, a cis regulatory region was localized between nucleotides -118 and -83, and Spl and adrenal-specific protein Correspondence to Y. Fujii-lriyama,

Mutant K-ras oncogene regulates steroidogenesis of normal human adrenocortical cells by the RAF-MEK-MAPK pathway

“…It also participates in the regulation of the cell response after the binding of growth factors with receptors (Bohm et al, 1995). Furthermore, CREB is a transcription factor for genes corresponding to steroidogenesis related enzymes (Watanabe et al, 1994;Kagawa et al, 1999). In this study, our laboratory proved that the mutant Ras protein enhanced not only the cell proliferation but also the steroidogenesis in steroidogenic phenotype cells by activation of Raf-MEK-MAPK signal transduction pathway.…”

A Novel Zinc Finger Protein TReP-132 Interacts with CBP/p300 to Regulate Human CYP11A1 Gene Expression

“…The orphan nuclear receptor SF-1 also known as adrenal binding protein (Ad4BP) has been demonstrated to promote cell specific expression of the human P450scc gene promoter in Y1 cells (19,21,22). The human P450scc gene promoter is inactive in nonsteroidogenic CV-1 cells, but could be activated by expression of exogenous SF-1 (21,23).…”

“…The cAMP-responsive element identified in human JEG-3 cells differs from the element identified when studies were performed in mouse Y1, MA-10, and I-10 cells (16,18). In these mouse cell lines, cAMPresponsive elements were localized to sites in the vicinity of nucleotides Ϫ1620 and Ϫ600, whereas cAMP response in JEG-3 cells was conferred by a proximal region around nucleotide Ϫ117 (18,19); however, neither of these elements were functional in NCI-H295 cells (17). Positive cis-acting elements have also been identified, which confer expression of P450scc gene promoter activity in steroidogenic cell lines, but not in nonsteroidogenic cells.…”

“…These putative cis-acting elements in the 5Ј-flanking region of the human P450scc gene have been demonstrated to interact with multiple proteins, which include CREB/ATF (19), NF1-and Sp1-like proteins, and in particular the steroidogenic factor-1 (SF-1). The orphan nuclear receptor SF-1 also known as adrenal binding protein (Ad4BP) has been demonstrated to promote cell specific expression of the human P450scc gene promoter in Y1 cells (19,21,22).…”

Cyclic AMP Stimulates SF-1-Dependent CYP11A1 Expression through Homeodomain-Interacting Protein Kinase 3-Mediated Jun N-Terminal Kinase and c-Jun Phosphorylation

“…Other partner molecules probably also participate in gene activation by cAMP. Proteins such as CREB/ATF that bind to the cAMP-responsive sequence can be likely candidates (55).…”