Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adrenodoxin reductase (AR; ferridoxin: NADP+ oxidoreductase, EC 1.18.1.2) is a flavoprotein that mediates electron transport from NADPH to all known mitochondrial forms of cytochrome P450. AR mRNA was found in all human adult and fetal tissues examined; however, it was vastly more abundant in tissues that synthesize steroid hormones. The ratio of the 18- form of mRNA lacking 18 alternately spliced bases to the 18+ form was approximately 100:1 and remained constant irrespective of the tissue or hormonal manipulation, indicating that the alternate splicing is a passive nonregulated event. AR protein was unchanged by forskolin treatment of human JEG-3 cytotrophoblast cells for 24 h, but the mRNA diminished. Phorbol 12-myristate 13-acetate and cycloheximide had no effect, even though these agents had the expected effects on P450scc and adrenodoxin mRNAs. cAMP decreased the abundance of AR mRNA expressed from both transfected plasmids and the endogenous gene, indicating the effect was post-transcriptional. AR gene transcription in JEG-3 cells and promoter-chloramphenicol acetyltransferase constructs transfected into JEG-3 cells were unresponsive to forskolin. Powerful basal transcription elements were identified between -46 and -214 bases from the principal transcriptional initiation site, a region containing six elements closely resembling the binding site for transcription factor SP1.
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PMID:cAMP post-transcriptionally diminishes the abundance of adrenodoxin reductase mRNA. 131 50

Long-term regulation of mammalian steroid hormone synthesis occurs principally by transcriptional regulation of the gene for the rate-limiting cholesterol side-chain cleavage enzyme P450scc. Adrenal steroidogenesis is regulated primarily by two hormones: adrenocorticotropin, which works via cyclic AMP (cAMP) and protein kinase A, and angiotensin II, which works via Ca2+ and protein kinase C. Forskolin and 8-bromo-cAMP stimulated, while prolonged treatment with a phorbol ester (12-O-tetradecanoylphorbol-13-acetate [TPA]) and a calcium ionophore (A23187) additively suppressed accumulation of endogenous P450scc mRNA in transformed murine adrenal Y1 cells. In Y1 cells transfected with 2,327 base pairs of the human P450scc promoter fused to the bacterial gene for chloramphenicol acetyltransferase (CAT), forskolin increased CAT activity 900% while combined TPA plus A23187 reduced CAT activity to 15% of the control level. Forskolin induced the P450scc promoter as rapidly as a promoter containing two cAMP-responsive elements fused to a simian virus 40 promoter, a system known to respond directly to cAMP. Basal expression was increased by sequences between -89 and -152 and was increased further by sequences between -605 and -2327. This upstream region also conferred inducibility by cAMP. TPA plus A23187 transiently increased CAT activity before repressing it, reflecting the complex actions of angiotensin II in vivo. Repression by prolonged treatment with TPA plus A23187 was mediated by multiple elements between -89 and -343. Induction of CAT activity by forskolin was not diminished by treatment with TPA plus A23187, nor were the regions of the promoter responsible for regulation by the two pathways coisolated. Thus, the human gene for P450scc is repressed by TPA plus A23187 by mechanisms and sequences independent of those that mediate induction by cAMP.
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PMID:Human P450scc gene transcription is induced by cyclic AMP and repressed by 12-O-tetradecanoylphorbol-13-acetate and A23187 through independent cis elements. 170 Feb 77

The mechanism of regulatory expression of human cytochrome P-450scc gene by cAMP was investigated in a transient expression system using Y-1 cells (mouse adrenal tumor cell line) and a chimeric DNA composed of the structural gene for bacterial chloramphenicol acetyltransferase and the 5' flanking upstream sequence of the cytochrome P-450scc (cholesterol desmolase) gene which was revealed to contain a DNA element(s) responsive to cAMP [Inoue, H. et al. (1988) Eur. J. Biochem. 171, 435-440]. Introduction of deletions and point mutations in the upstream regulatory sequence demonstrated that three regions were mainly required for response to cAMP. These regions contained a short similar sequence. All of them have a 5-bp motif GTCAT (or ATGAC) in common, and have at least two motifs which conserve four out of five base pairs of the consensus sequence of the cAMP-responsive element (CRE), CGTCA (or TGACG). They are all apparently necessary for regulation by cAMP. Gel mobility shift assays suggested that a binding factor(s) to these regions was present in the nuclear extracts of Y-1 cells and adrenal cortex tissues and appeared to be different from the somatostatin CRE-binding protein. Deletion analysis also suggested that the region around -44 was essential to the basal transcriptional activity. This region shows some similarity to the CTF NF-1 binding site [Johnson and McKnight (1989) Annu. Rev. Biochem. 58, 799-839].
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PMID:Structures of regulatory regions in the human cytochrome P-450scc (desmolase) gene. 184 89

Progesterone is essential to the sustenance of pregnancy in humans and other mammals. From the second trimester on, the human placenta is the sole origin of de novo synthesized steroid hormones. In mice, placentation at midgestation is accompanied by a temporal rise of steroid hormone synthesis commencing in the giant cells of the mouse trophoblast. In doing so, the giant trophoblasts, as any other steroidogenic cell, express high levels of the key steroidogenic enzyme, cholesterol side-chain cleavage cytochrome P450 (P450scc). Because steroidogenic factor 1 (SF-1), the transcription factor required for expression of P450scc in the adrenals and the gonads, is not expressed in the placenta, we hypothesized that placenta-specific nuclear factor(s) (PNF) assumes the role of SF-1 by binding to the same promoter region that harbors the SF-1 recognition site in the P450scc gene. To address this possibility, we used SCC1, a well conserved proximal region in the P450scc genes (-60/-32 in the rat gene) to purify PNF from human term placenta. Sequencing of the purified PNF revealed that it is the alpha isoform of the human activating protein-2 (AP-2alpha). Specific antibodies tested in EMSA confirmed that AP-2alpha is the predominant isoform that binds SCC1 in the human placenta, whereas AP-2gamma is the only mouse placental protein that binds this oligonucleotide. Functional studies showed that coexpression of the rat P450scc promoter (-378/+8 CAT) and AP-2 isoforms (alpha or gamma) in human embryonic kidney 293 cells results in a marked activation of chloramphenicol acetyltransferase (CAT) transcription that is dependent on an intact AP-2 motif, GCCTTGAGC. This motif conforms with consensus sequences previously determined for binding of the AP-2 alpha and gamma isoforms. Mutations of the AP-2 element ablated binding of AP-2 to SCC1, as well as severely diminished the promoter activity in primary mouse giant trophoblasts and human choriocarcinoma JAR cells. Collectively, these studies suggest that expression of placental P450scc is governed by AP-2 factors that bind to a cis-element that largely overlaps the sequence required for recognition of SF-1 in other steroidogenic tissues.
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PMID:Transcription of cholesterol side-chain cleavage cytochrome P450 in the placenta: activating protein-2 assumes the role of steroidogenic factor-1 by binding to an overlapping promoter element. 1214 40