Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

The proximal 5'-flanking region of the alpha-subunit gene from humans and cattle confers pituitary-specific expression to heterologous reporter genes in transgenic mice. To investigate whether these promoter regions also contain the necessary regulatory elements for cell-specific expression and hormonal regulation, we used three independent lines of transgenic mice. Two lines of transgenic mice contained chimeric genes consisting of either 1.6 kilobasepairs (kbp) of human or 3 15 basepairs of bovine alpha-subunit proximal 5'-flanking sequence linked to the bacterial gene encoding chloramphenicol acetyltransferase (CAT). A third line of transgenic mice contained the proximal 1.6 kbp of 5'-flanking sequence of the human alpha-subunit gene linked to the bacterial lacZ gene encoding beta-galactosidase (beta gal; H alpha beta gal transgenic mice). Hormonal replacement paradigms indicate that both human and bovine alpha CAT transgenes are regulated by GnRH, suggesting that their expression occurs in gonadotropes. Thus, the proximal 5'-flanking regions of both the human and bovine alpha-subunit genes must contain regulatory elements that confer both gonadotrope-specific expression and responsiveness to GnRH. In contrast to the human alpha-subunit promoter, the bovine alpha-subunit promoter lacks a functional cAMP response element, suggesting that transduction of both cell-specific and GnRH transcriptional signals occurs through cAMP response element-independent pathways. Thyrotropes also express the glycoprotein hormone alpha-subunit gene. Yet, hormone replacement paradigms with propylthiouracil and T3 were ineffective in altering CAT activity in the pituitary of human or bovine alpha CAT transgenic mice. Because a thyroid hormone response element has been localized to the proximal 5'-flanking region of the human alpha-subunit gene, these data suggest that the alpha CAT transgenes lack sufficient information to direct expression to thyrotropes. Direct evidence for this possibility was obtained through immunocytochemical studies performed on pituitaries from H alpha beta gal transgenic mice. beta-Galactosidase activity appeared in gonadotropes, but not thyrotropes. We conclude, therefore, that distinct and separable regulatory elements mediate the expression of the alpha-subunit gene in gonadotropes and thyrotropes.
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PMID:Gonadotrope- and thyrotrope-specific expression of the human and bovine glycoprotein hormone alpha-subunit genes is regulated by distinct cis-acting elements. 128 Mar 29

Adenovirus infection of hepatoma cells inhibited transcription of the phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.1.32) (PEPCK) gene and virtually eliminated transcription of a chimeric gene which contained the PEPCK promoter linked to the structural gene for chloramphenicol acetyltransferase (CAT). This effect is due to the viral protein E1A, since adenovirus containing a deletion in the E1A gene did not repress transcription from the PEPCK promoter. Both the 243R and 283R products of the E1A gene were effective. The conserved region 1 (CR-1) domain of E1A was required for this effect. Treatment of hepatoma cells with 8-bromo-cAMP or transfection with plasmids coding for the catalytic subunit of protein kinase A, CAAT/enhancer binding protein alpha (C/EBP), or Jun, all potent inducers of PEPCK gene transcription, did not relieve the inhibition caused by E1A. This inhibition does not appear to be mediated by major enhancer elements and in the PEPCK gene since transcription from the PEPCK promoter containing block mutations in binding domains for C/EBP and cAMP regulatory element binding protein (CREB) was also inhibited by E1A. Transcription of chimeric genes containing two copies each of the major cAMP response domains (CRE-1 and P-3) linked to a neutral promoter and fused to the CAT structural gene was stimulated by the catalytic subunit of protein kinase A, but this effect was totally inhibited by E1A. The strong repressive effect of E1A on PEPCK gene transcription seems to involve an interruption of an obligatory interaction between factors which bind to the cAMP response element in the PEPCK promoter and the TATA box.
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PMID:Adenovirus E1A represses the cyclic AMP-induced transcription of the gene for phosphoenolpyruvate carboxykinase (GTP) in hepatoma cells. 131 Mar 18

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

A rat genomic clone containing 4.5 kilobases of 5'-flanking DNA and the first exon of the type II beta regulatory subunit (RII beta) of cAMP-dependent protein kinase was isolated, restriction mapped, and sequenced. The proximal 400-basepair promoter region was GC rich, lacked TATA/CAAT box motifs, and initiated transcription at multiple sites. Bandshifting and DNase-I footprinting experiments using this region of the RII beta promoter detected several related specific DNA-protein complexes formed using crude and fractionated nuclear extracts from rat ovary, brain, adrenal gland, and liver. All binding in these experiments mapped to a domain within the same region found to confer cAMP inducibility to a chloramphenicol acetyltransferase (CAT) reporter gene when transfected into primary cultures of rat granulosa cells. Although GC boxes (putative SP1-binding sites) and activator protein-2 (AP-2) elements were present in this functional region, and although expression vectors containing AP-2 sites conferred high levels of cAMP regulation of the CAT gene in cultured ovarian cells, neither the GC boxes nor the AP-2 sites were protected by footprint analyses or required for band shift activity of nuclear extract protein. These known regulatory elements, therefore, may be involved in functional activity of the RII beta promoter, but additional cis-acting DNA and trans-acting factors (yet to be characterized) also appear to interact with the functional promoter of the RII beta gene and regulate the hormone-specific expression of the A-kinase subunit in ovarian and neuronal cells.
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PMID:Identification and characterization of the GC-rich and cyclic adenosine 3',5'-monophosphate (cAMP)-inducible promoter of the type II beta cAMP-dependent protein kinase regulatory subunit gene. 131 46

Human progesterone receptors (PR) in T47D breast cancer cells are synthesized as two different sized proteins, PR-A [94 kilodaltons (kDa)] and PR-B (120 kDa). Progestin addition to cells (in vivo) causes a 2-fold increase in total phosphorylation of PR and an increase in the apparent mol wt of both PR-A and PR-B on sodium dodecyl sulfate (SDS)-gels. Time-course experiments showed that increased PR phosphorylation that results from hormone addition is a multistep process and involves a rapid increase into total 32P labeling that takes place before the more slowly occurring phosphorylation(s) responsible for the change in electrophoretic mobility of PR on SDS-gels. As an approach to test whether phosphorylation is involved in regulating PR activity, we have examined the effects of cellular modulators of protein phosphorylation on PR-mediated target gene transcription in vivo using a T47D cloned cell line containing a stably transfected mouse mammary tumor virus-chloramphenicol acetyltransferase construct. Treatment with 8-bromo-cAMP (activator of cAMP-dependent protein kinases) or okadaic acid (protein phosphatase-1 and -2A inhibitor) did not stimulate target gene expression in the absence of progestin. When added together with progestin, either compound augmented PR-mediated target gene transcription by 3- to 4-fold. The cyclic nucleotide-dependent protein kinase inhibitor H8 completely blocked target gene responsiveness to hormone. Neither 8-bromo-cAMP, okadaic acid, nor H8 altered the hormone- or DNA-binding activities of PR, as measured in vitro or affected cellular concentrations of PR. These agents, therefore, appeared to selectively modulate PR transcriptional activity. Moreover, none of these compounds altered expression from a control reporter gene, pSV2CAT, indicating that these agents affect PR-mediated processes directly and are not acting through a general effect on transcription. Effects on PR phosphorylation were assessed by measuring 32P labeling of PR in vivo. None of these treatments had a substantial effect on the extent of total 32P labeling of immune isolated PR or on the phosphorylation(s) responsible for PR up-shifts on SDS-gels. This suggests that these agents modulate PR transcriptional activity either through phosphorylation of another protein intimately involved in PR-mediated transcription or through modification of a key site(s) not measurable as a change in total PR phosphorylation or electrophoretic mobility on SDS gels.
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PMID:Effects of hormone and cellular modulators of protein phosphorylation on transcriptional activity, DNA binding, and phosphorylation of human progesterone receptors. 131 49

The biosynthesis in Leydig cells of the C19 steroid testosterone from the C21 precursor progesterone requires the activities of the enzyme cytochrome P450 17 alpha-hydroxylase/C17-20 lyase (P450(17 alpha)). Previous studies from this laboratory demonstrated that the de novo synthesis of the P450(17 alpha) protein and the accumulation of P450(17 alpha) mRNA in mouse Leydig cell cultures is absolutely dependent on cAMP stimulation. To investigate further the cAMP regulation of P450(17 alpha) expression in Leydig cells, the structural gene encoding P450(17 alpha) (Cyp17) was isolated from a mouse genomic library using a full-length mouse P450(17 alpha) cDNA. Two overlapping genomic clones were isolated and characterized by restriction mapping and partial sequencing. The two clones together contain the entire coding region and approximately 10 kilobases of 5'-flanking sequences of Cyp17. To identify regions necessary for cAMP-induced transcription, 5'-flanking regions of Cyp17 were fused with the chloramphenicol acetyltransferase (CAT) reporter gene and transiently transfected into MA-10 tumor Leydig cells. Studies localized the cAMP-responsive region of the gene to a region between -346 and -245 basepairs relative to the transcription initiation site. Transient transfections of MA-10 cells with a construct consisting of the -346/-245 sequences fused to a heterologous promoter, thymidine kinase, and the CAT reporter gene demonstrated a marked increase in cAMP stimulation of CAT expression, providing additional evidence that the -346/-245 sequences of the Cyp17 5'-flanking region confer cAMP-induced expression of Cyp17. This cAMP-responsive region of mouse Cyp17 bears no apparent homology to the cAMP-responsive regions identified in the human and bovine Cyp17 genes.
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PMID:Isolation and characterization of the mouse P450 17 alpha-hydroxylase/C17-20-lyase gene (Cyp17): transcriptional regulation of the gene by cyclic adenosine 3',5'-monophosphate in MA-10 Leydig cells. 132 57

We have investigated the functional elements involved in cAMP-stimulated transcription of the human ferredoxin gene. Unlike the bovine gene, the human gene lacked a second upstream RNA initiation site as demonstrated by sequence analysis of the exon boundary, lack of upstream RNA, and analysis of the promoter. The presence of a single promoter was determined by testing the ability of various gene segments to drive the expression of the chloramphenicol acetyltransferase gene after transfection into a mouse adrenal cell line Y1. Full promoter activity was conferred by a DNA fragment spanning -209 to +55, although the -94 to +55 fragment already provided some promoter activity. Transcription from the -94 to +55 segment was stimulated by 2-fold when 8-bromo-cAMP was added to the cell. Footprinting analyses showed two GC boxes at -50 to -70 and -87 to -108 were protected by proteins from both Y1 and HeLa cells. Competition experiments showed that a protein with a recognition sequence indistinguishable from Sp1 bound to these sites. When connected to a heterologous TATA box, the sequence at -76 to -42, which contained the proximal GC box, was able to confer a high level of basal transcription and cAMP stimulation. This sequence does not show sequence homology with the known cAMP-responsive element. Mutations or deletion of the Sp 1-binding site showed diminished basal transcription and defined the cAMP responsive sequence to be from -76 to -62. Therefore the cAMP-responsive sequence of the human ferredoxin gene was located at -76 to -62, which was adjacent to the Sp 1-binding site.
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PMID:Transcription of the human ferredoxin gene through a single promoter which contains the 3',5'-cyclic adenosine monophosphate-responsive sequence and Sp 1-binding site. 133 72

The "minimal" promoter region of the TSH receptor gene, -195 to -39 basepairs (bp), exhibits basal promoter activity, thyroid specificity, and negative regulation by TSH via its cAMP signal. In FRT thyroid cells and by comparison to pTRCAT5'-199, 5'-deletion mutants of chloramphenicol acetyltransferase (CAT) constructs from -199 to -150 bp of the minimal promoter decrease basal CAT activity by 50%, whereas continued deletion to -146 bp increases activity more than 4-fold. Continued deletion to -131 bp results in basal activity less than that of the -199 bp construct. An octameric cAMP response element (CRE)-like sequence, TGAGGTCA, is within -146 to -131 bp and starts at -139 bp. Its mutation to a consensus CRE (TGACGTCA) or AP1 (TGAGTCA) site or mutation of several residues flanking its 3'-terminus can improve promoter activity as much as 8-fold compared to pTRCAT5'-199. A nonpalindromic mutation to CGAGGACA decreases basal promoter activity to the level of the 199-bp minimal promoter. The CRE-like sequence between -139 and -132 bp is a constitutive enhancer of promoter activity in FRT thyroid cells, since, ligated to a simian virus-40-promoter-driven CAT gene, it increases CAT activity in the absence of forskolin in proportion to copy number and independent of direction or position. It can, however, function as a cAMP-responsive CRE, as evidenced by the fact that forskolin increases the activity of the same simian virus-40-promoter-driven CAT gene constructs in Buffalo rat liver (BRL) cells. DNAase-I footprinting shows that the CRE region is protected by a purified binding region peptide of the CRE-binding protein, activating transcription factor-2, and recombinant AP1 (human c-jun) as well as by BRL, FRT, and FRTL-5 rat thyroid cell nuclear extracts. Gel mobility shift analyses show that multiple CRE-binding proteins in the BRL, FRT, and FRTL-5 cell nuclear extracts form complexes with the CRE-like site, that one of these is CRE-binding protein, and that all form complexes with mutant sequences of the CRE-like site in a manner that exactly parallels their effects on constitutive enhancer function in FRT thyroid cells. We show, therefore, that the CRE-like site in the minimal TSH receptor promoter functions as a constitutive enhancer of promoter activity in FRT thyroid cells yet is a cAMP-responsive CRE.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Role of the cyclic adenosine 3',5'-monophosphate response element in efficient expression of the rat thyrotropin receptor promoter. 133 54

The thyroid follicular cell requires elevated levels of cAMP for normal growth and optimal expression of the differentiated phenotype. The recent discovery of cAMP-regulated enhancer binding (CREB) proteins prompted us to analyze the possible role of these transcription factors in controlling thyroid cell growth and differentiated phenotype using the FRTL5 thyroid cell line as a model system. FRTL5 cells were stably transfected with an expression vector containing either the gene for wild type CREB (WTCREB) or a dominant negative mutant form of CREB, termed KCREB, which dimerizes with and inactivates endogenous CREB. Transfected clones were found to express the transfected KCREB and WTCREB mRNAs at higher levels than the endogenous CREB mRNA. Transient expression of a somatostatin-chloramphenicol acetyltransferase fusion gene in these clones demonstrated a 60% reduction of cAMP-regulated enhancer-dependent transcriptional activity in the KCREB transfected clones and wild type levels of activity in the WTCREB transfected clones. Parameters of growth (DNA synthesis and growth rate) and differentiation (iodide uptake and thyroglobulin mRNA levels) were then analyzed in the transfected clones. Transfection of WTCREB had no effect on any of the parameters examined in comparison to untransfected cells, presumably because CREB is already constitutively expressed at maximal levels in normal FRTL5 cells. However, cells expressing KCREB showed an 18-40% reduction in TSH-stimulated thymidine incorporation, a 31% increase in the length of the cell cycle, and a 4-fold reduction in TSH-stimulated iodide uptake in comparison with wild type cells or cells tranfected with wild type CREB.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:3',5'-cyclic adenosine monophosphate-regulated enhancer binding (CREB) activity is required for normal growth and differentiated phenotype in the FRTL5 thyroid follicular cell line. 133 55

Transcription of the rat serine dehydratase (SDH) gene is induced by glucagon, mediated by the action of cAMP. To identify the nucleotide sequences in the SDH gene responsible for this regulation, we constructed chimeric genes containing different portions of the 5' flanking region of the rat SDH gene fused to the structural sequence encoding the bacterial reporter enzyme, chloramphenicol acetyltransferase (CAT). The transcriptional activities of the fusion genes introduced into the rat hepatoma cell line 7AD-7 were assayed by measuring CAT activity in the cell lysates. Chlorophenylthio-cyclic AMP (CPT-cAMP), a potent protein kinase A activating agent, stimulated the expression of SDH-CAT fusion genes, and these inductions could be enhanced further by the addition of dexamethasone, although the glucocorticoid alone had no effect on CAT activity. Deletion analysis demonstrated that an 80 bp region located approximately 3.5 kb upstream from the transcription initiation site of the rat SDH gene was responsible for stimulation of transcription by CPT-cAMP, whereas the 120 bp region immediately upstream of the cAMP responsive element (CRE)-containing sequences is essential for the enhancement of CPT-cAMP induction by the glucocorticoid.
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PMID:Identification of regions in the rat serine dehydratase gene responsible for regulation by cyclic AMP alone and in the presence of glucocorticoids. 133 28


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