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)

In C57BL/6 mouse liver, both murine Cypla-1 (cytochrome P1(450] and Cypla-2 (P3(450] genes are inducible by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dioxin), and Cypla-2 is constitutively expressed at high levels. Although the Cypla-1 gene is constitutively expressed and TCDD-inducible in mouse hepatoma Hepa-1 cell cultures, Cypla-2 gene expression is absent in these cultures. We show here that the 5' flanking region of Cyp1a-2 from - 1843 to +52 (base pairs relative to the Transcription initiation site) linked to the chloramphenicol acetyltransferase (CAT) reporter gene in stable Hepa-1 transformants produces no basal or TCDD- or cycloheximide-inducible CAT activity. On the other hand, the Cyp1a-2 promoter from -63 to +52 driving the CAT gene is inducible by cycloheximide. A chimeric plasmid containing the Cyp1a-1 TCDD-responsive enhancer (-1646 to -245) ligated to a Cyp1a-2 promoter region (-129 to +52) supports TCDD-inducible CAT expression in Hepa-1 cells and in rat 7777 cells. These data suggest that, although sequences between - 1843 and +52 +52 are not sufficient for Cyp1a-2 gene expression, the murine Cyp1a-2 promoter is functional in cell cultures.
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PMID:Expression of the chloramphenicol acetyltransferase (CAT) reporter gene by the murine Cyp1a-2 (cytochrome P3(450)) promoter in hepatoma cell cultures. 217 15

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is known to interact with a cytosolic receptor and, in turn, activate transcription of the mouse P1(450) gene. Various lengths of DNA upstream of the P1(450) gene were inserted into the pSV0-cat expression vector, with and without addition of the Harvey murine sarcoma virus (Ha-MSV) 72-bp repeat enhancer element. The constructs were cotransfected with pSV2-neo into mouse hepatoma wild-type cells and two variant cell lines. One variant is believed to result from a mutation in the P1(450) structural gene and expresses high levels of P1(450) mRNA constitutively; the other variant has a defect in nuclear translocation of the inducer-receptor complex. After selection in G418, the cells were treated with control medium, TCDD, cycloheximide, or TCDD plus cycloheximide and then assayed for chloramphenicol acetyltransferase (CAT) activity. The data are consistent with the presence of several functional regions within the upstream sequence: a promoter region, a region that is negatively autoregulated, possible repressor-binding and inducer-receptor complex-binding sites, and an upstream activation element that is required for transcriptional activation by TCDD. The Ha-MSV enhancer can substitute for this upstream activation element.
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PMID:Autoregulation plus upstream positive and negative control regions associated with transcriptional activation of the mouse P1(450) gene. 299 46

We have studied the effect of several environmental chemicals on the transient expression of a chloramphenicol acetyltransferase (cat) reporter gene linked to the promoter sequences in the long terminal repeat (LTR) of the human immunodeficiency virus type 1 (HIV-1). Aflatoxin B1, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dioxin) and benzo[a]pyrene cause a significant increases in CAT expression in mouse hepatoma Hepa-1 cells. The induction of CAT after TCDD treatment is abolished by administration of N-acetyl-L-cysteine or 2-mercaptoethanol and does not take place in a mutant cell line that lacks CYP1A1 enzymatic activity. Linker-scanning mutational analysis of transcription factor binding sites in the promoter revealed that both the NF kappa B and an adjacent aromatic hydrocarbon response element (AhRE) are required for TCDD-dependent CAT expression. In addition, mutation of the NFAT/AP-1 binding sites in the negative regulatory region of the promoter increases the magnitude of the TCDD effect. We conclude that induction of a functional CYP1A1 monooxygenase by TCDD stimulates a pathway that generates thiol-sensitive reactive oxygen intermediates which, in turn, are responsible for the TCDD-dependent activation of genes linked to the LTR. These data might provide an explanation for findings that TCDD increases infectious HIV-1 titers in experimental systems and for epidemiologic reports suggesting that exposure to aromatic hydrocarbons, such as found in cigarette smoke, is associated with an acceleration in AIDS progression.
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PMID:Dioxin activates HIV-1 gene expression by an oxidative stress pathway requiring a functional cytochrome P450 CYP1A1 enzyme. 760 37

17 beta-Estradiol (E2) induces cathepsin D mRNA levels and intracellular levels of immunoreactive protein in MCF-7 human breast cancer cells. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) alone does not affect cathepsin D gene expression in this cell line; however, in cells cotreated with TCDD and E2, TCDD inhibited E2-induced cathepsin D mRNA levels, the rate of gene transcription, and levels of immunoreactive protein. The inhibitory responses were observed within 30 to 120 min after the cells were treated with TCDD. TCDD also inhibited E2-induced secreted alkaline phosphatase activity in aryl hydrocarbon (Ah)-responsive MCF-7 and wild-type mouse Hepa 1c1c7 cells cotransfected with the human estrogen receptor (hER) and the pBC12/S1/pac plasmid, which contains the 5' promoter region (-296/+57) of the cathepsin D gene and an alkaline phosphatase reporter gene. The E2-responsive ER/Sp1 sequence (-199 to -165) in the cathepsin D 5' region contains an imperfect GTGCGTG (-175/-181) xenobiotic responsive element (XRE); the role of this sequence in Ah responsiveness was investigated in gel electrophoretic mobility shift assays and with plasmid constructs containing a wild-type ER/Sp1 oligonucleotide or a mutant ER/Sp1-"XRE" oligonucleotide containing two C-->A mutations in the XRE sequence (antisense strand). In plasmid constructs which contained a chloramphenicol acetyltransferase reporter gene and the wild-type ER/Sp1 promoter sequence, E2-induced chloramphenicol acetyltransferase activity and mRNA levels were inhibited by TCDD whereas no inhibition was observed with the mutant ER/Sp1-"XRE" plasmids. Electrophoretic mobility shift assays showed that the nuclear or transformed cytosolic Ah receptor complex blocked formation of the ER-Sp1 complex with the wild-type but not the ER/Sp1 mutant oligonucleotide. Moreover, incubation of the wild-type bromodeoxyuridine-substituted ER/Sp1 oligonucleotide with the nuclear Ah receptor complex gave a specifically bound cross-linked 200-kDa band. These data demonstrate that Ah receptor-mediated inhibition of E2-induced cathepsin D gene expression is due to disruption of the ER-Sp1 complex by targeted interaction with an overlapping XRE.
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PMID:Molecular mechanism of inhibition of estrogen-induced cathepsin D gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in MCF-7 cells. 852 36

Transcriptional regulation of human UGT1A6, a UDP glucuronosyltransferase isoform conjugating a wide variety of planar phenols, has been studied using transfection experiments with plasmids containing its 3-kb 5' upstream region and chloramphenicol acetyltransferase as reporter gene. Previously, two modes of expression of the isoform have been described: in colon carcinoma Caco-2 cells UGT1A6 was found to be TCDD-inducible, whereas in lung carcinoma A549 cells it was constitutively expressed. Therefore functional analysis of UGT1A6 regulation was carried out using these two cell lines. In the upstream region of human UGT1A6 one xenobiotic-responsive element (XRE) was found between-1498 and -1502 bp. In Caco-2 cells the reporter gene activity of the entire plasmid and of deletion mutants containing the XRE were TCDD-inducible, in contrast to experiments with a deletion mutant which did not contain the XRE. TCDD induction was marginal in transfection studies with A549 cells. Gel mobility shift analysis indicated that the aryl hydrocarbon receptor and its partner Arnt bind to the XRE. Furthermore, primer extension studies suggest cell-specific use of multiple TATA boxes. Hence, regulation of human UGT1A6 appears to be cell-specific including both constitutive and aryl hydrocarbon receptor-controlled expression.
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PMID:Aryl hydrocarbon receptor-inducible or constitutive expression of human UDP glucuronosyltransferase UGT1A6. 946 22

17Beta-estradiol (E2) induced c-fos protooncogene mRNA levels in MCF-7 human breast cancer cells, and maximal induction was observed within 1 h after treatment. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) inhibited the E2-induced response within 2 h. The molecular mechanism of this response was further investigated using pFC2-CAT, a construct containing a -1400 to +41 sequence from the human c-fos protooncogene linked to a bacterial chloramphenicol acetyltransferase (CAT) reporter gene. In MCF-7 cells transiently transfected with pFC2-CAT, 10 nM E2 induced an 8.5-fold increase of CAT activity, and cotreatment with 10 nM TCDD decreased this response by more than 45%. Alpha-Naphthoflavone, an aryl hydrocarbon receptor (AhR) antagonist, blocked the inhibitory effects of TCDD; moreover, the inhibitory response was not observed in variant Ah-nonresponsive MCF-7 cells, suggesting that the AhR complex was required for estrogen receptor cross-talk. The E2-responsive sequence (-1220 to -1155) in the c-fos gene promoter contains two putative core pentanucleotide dioxin-responsive elements (DREs) at -1206 to -1202 and -1163 to -1159. In transient transfection assays using wild-type and core DRE mutant constructs, the downstream core DRE (at -1163 to -1159) was identified as a functional inhibitory DRE. The results of photo-induced cross-linking, gel mobility shift, and in vitro DNA footprinting assays showed that the AhR complex interacted with the core DRE that also overlapped the E2-responsive GC-rich site (-1168 to -1161), suggesting that the mechanism for AhR-mediated inhibitory effects may be due to quenching or masking at the Sp1-binding site.
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PMID:Transcriptional activation of c-fos protooncogene by 17beta-estradiol: mechanism of aryl hydrocarbon receptor-mediated inhibition. 1047 42

TCDD is known to reduce significantly the level of the functionally active form of glucose transporter type 4 (GLUT4) in vivo in adipose tissue and muscles. To study the mechanistic basis of this phenomenon, we conducted transient transfection and DNA deletion analysis in 3T3-L1 cells using chloramphenicol acetyltransferase (CAT) reporter plasmids containing the GLUT4 promoter joined to the bacterial CAT. It was found that in transfected control samples, CAT activity was significantly higher in cells transfected with p469CAT and p273CAT than those with p78CAT, indicating that the region between -78 and -273 contained elements that play major roles in transactivation of this gene. Treatment with TCDD decreased CAT activity with p469CAT and p273CAT, but not with p78CAT, indicating the same region to contain the element(s) affected by TCDD. A gel-shift (EMSA) analysis result indicated that TCDD shows the profound effect only on the nuclear proteins binding to the [(32)P]-labeled probe containing C/EBP response element equivalent of the -265 to -242 stretch of the GLUT4 promoter. The results of supershift analysis showed that TCDD caused a decrease in the tier of C/EBPalpha and an increase in that of C/EBPbeta among the proteins bound to this C/EBP response element. We studied the effect of TCDD in cells overexpressing either C/EBPalpha, C/EBPbeta, or C/EBPdelta through transient transfection of p273CAT or p469CAT. The results clearly showed that the effect of TCDD to suppress the CAT activity of p273 or p469 disappeared in those cells overexpressing C/EBPalpha or C/EBPbeta. These results implicate the C/EBP proteins to be the main mediator of suppressive action of TCDD on GLUT4 gene expression in 3T3-L1 cells.
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PMID:TCDD suppresses insulin-responsive glucose transporter (GLUT-4) gene expression through C/EBP nuclear transcription factors in 3T3-L1 adipocytes. 1661 95

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