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)

A strong enhancer element, GPEI, of the glutathione transferase P gene (GST-P) gene is composed of two phorbol 12-O-tetradecanoate 13-acetate (TPA) responsive element (TRE)-like sequences at opposite orientation. Unlike TRE sequences of other genes, GPEI exhibits a strong enhancer activity in F9 cells, which contains little AP-1. GPEI bound to AP-1 In vitro and GST-P expression was activated by TPA and exogenously introduced c-jun gene in a rat fibroblast cell line. Both the stimulated expression of GST-P gene by TPA and that by over-expressed c-Jun were suppressed to the basal level by dexamethasone, an inhibitor of AP-1. Basal expression of GST-P gene, however, was not inhibited by dexamethasone. Transfected chloramphenicol acetyltransferase (CAT) gene having GPEI also behaved as the endogenous GST-P gene. These results indicate that the GPEI is activated by AP-1 but constitutive activity of this enhancer in a rat fibroblast cell line 3Y1 cells is due to some unknown mechanism other than AP-1.
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PMID:Suppression of glutathione transferase P expression by glucocorticoid. 153 Jun 52

By means of transgenic rats, we have recently shown that the GPEI enhancer of the glutathione transferase P (GST-P) gene, which has two one-base-missmatched AP-1 sites locating palindromically with three-base spacing in between, is sufficient for conferring tumor-specific activation of the gene in vivo. It is noted that there is another consensus AP-1 site near the promoter of this gene. By using seven independent transgenic rats, bearing distinct areas of the GST-P gene that are connected to the chloramphenicol acetyltransferase (CAT) coding sequence, we analyzed CAT expression in various tissues (brain, lung, liver, kidney, spleen) in these transgenic rats. We found that the ECAT gene, which has sufficient of the upstream regulatory region (approx. 2.9 kb) of the gene containing GPEI, is trans-activated in the kidney and lung of transgenic rats in a similar manner to endogenous GST-P. When either the GPEI core sequence or the AP-1 site near the promoter is deleted, CAT expression decreases to almost background level. Substitution of the GPEI core or the AP-1 site near the promoter to this silent construct (5CATGPEIcore) reconstituted CAT expression in the transgenic rats. In these rats, CAT was expressed in the brain and lung rather than in the kidney, showing a somewhat different pattern from the endogenous GST-P. In the brain tissue of the 5CATGPEIcore transgenic rat, CAT was demonstrated in the glia cells, which is consistent with endogenous GST-P expression. These results suggest that a relatively long upstream region (approx. 2.9 kb) is required for tissue-specific expression of the GST-P gene and that GST-P expression in the brain may be regulated differently from its expression in other organs.
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PMID:Tissue-specific activation of tumor marker glutathione transferase P transgenes in transgenic rats. 755 45

The glutathione transferase P (GST-P) gene is known for its specific expression during chemical hepatocarcinogenesis of the rat and is used as a tumor marker for hepatocellular carcinoma. We have shown recently that the upstream 2.9-kb region of the GST-P gene is sufficient for conferring tumor-specific expression of the gene in vivo (S. Morimura et al., Proc. Natl. Acad. Sci. USA, 90: 2065-2068, 1993). To further identify crucial sequence elements regulating the unique expression of this gene, we have established six independent lines of transgenic rats bearing distinct areas of the GST-P gene that are connected to the chloramphenicol acetyltransferase coding region and analyzed changes of the chloramphenicol acetyltransferase activity during the course of chemical hepatocarcinogenesis. We demonstrate here that the enhancer, glutathione transferase P enhancer I, that is located 2.5 kb upstream of the GST-P gene is required and sufficient for its tumor-specific expression of the gene among other controlling elements. This approach to transgene expression could be used to define other enhancers, the activity of which is dependent on cellular changes such as carcinogenesis, development, and differentiation.
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PMID:Identification of an enhancer responsible for tumor marker gene expression by means of transgenic rats. 778 Sep 80

Glutathione transferase P (GST-P; glutathione transferase, EC 2.5.1.18) is known to be specifically expressed at high levels in precancerous lesions and in hepatocellular carcinomas from a very early phase of chemically induced hepatocarcinogenesis in the rat. The almost invariable occurrence of this phenotype in these lesions strongly suggests a mechanism by which GST-P gene is activated together with a crucial transforming gene of liver cells. To distinguish the two alternative possibilities--either the GST-P gene is coactivated with a closely located transforming gene by a cis mechanism or it is activated in trans by a common trans-acting factor--we carried out carcinogenesis experiments using transgenic rats harboring the bacterial chloramphenicol acetyltransferase reporter gene ligated to the upstream regulatory sequence of the GST-P gene. In each of three independent lines tested, liver foci and nodules produced by chemical carcinogens (Solt-Farber procedure) were found to express high levels of chloramphenicol acetyltransferase activity, indicating clearly that the GST-P gene is activated by a trans mechanism during hepatocarcinogenesis.
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PMID:Trans-activation of glutathione transferase P gene during chemical hepatocarcinogenesis of the rat. 844 29

Rat glutathione transferase P (GST-P) is expressed at low levels in the normal liver but becomes highly expressed in hyperplastic nodules and in hepatocellular carcinomas during chemical hepatocarcinogenesis. To understand the regulation mechanisms of this gene, we have characterized the 5'-flanking region and have found that GST-P gene is regulated by at least two elements: one is a strong enhancer and the other is a silencer. GST-P enhancer I (GPEI), located at -2.5 Kb, consists of two TPA-responsive element (TRE)-like sequences that are palindromically oriented with 3 bp in between. It is well known that TRE is activated by two nuclear oncogenes, c-Jun and c-Fos. Although GPEI is trans-activated by these oncogenes, it is also active in F9 embryonal carcinoma cells that lack c-Jun protein, suggesting that it can function with some trans-activator other than AP-1 (c-Jun/c-Fos heterodimer). Indeed, another protein is identified from the F9 nuclear extract. We have also identified a silencer element at 300 bp upstream from the cap site. There are several cis-elements in this region and at least three trans-acting factors bind to these elements. We purified SF-A (silencer factor A) which binds to several regions in this silencer, and determined the partial amino acid sequence. Interestingly, SF-A seemed to be a related protein to NF1 (nuclear factor 1) which is an activator for the transcription and DNA replication. Another factor SF-B (silencer factor B) has been cloned and found to be the same as LIP (liver inhibitory protein) which is a competitor for LAP (liver activator protein), both are from the same gene designated as C/EBP beta. By transfection analysis using GAL4 DNA binding domain we found LIP is not only a competitor but a direct repressor. In the normal liver, another C/EBP family member, C/EBP alpha also acts as a negative regulator, and this expression decreases during hepatocarcinogenesis, resulting in the loss of silencer function. We carried out the carcinogenesis experiments using transgenic rats harboring a chloramphenicol acetyltransferase (CAT) reporter gene with -2900 to + 59 of the GST-P gene. Liver foci and nodules produced by chemical carcinogens were found to express high levels CAT activity by both CAT assay and immunohistochemical study, while normal liver cells did not express any CAT activity. These results demonstrate that the GST-P gene is trans-activated locus-independently during rat hepatocarcinogenesis. Moreover, the similar results were obtained using transgenic rats carrying GPEI-CAT, indicating that GPEI is an important cis-element for activation of GST-P gene during hepatocarcinogenesis.
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PMID:[Regulation mechanism of specific expression of tumor marker gene during carcinogenesis]. 883 Dec 56

In the present study, we analysed the expression of monooxygenase activities and mRNAs associated with cytochrome P-450 (CYP), including CYP1A1/2, CYP2B1/2, CYP2C6, CYP2E1, CYP3A1/2, glutathione transferase alpha (GST alpha), aldehyde dehydrogenase and epoxide hydrolase in co-cultures of primary rat hepatocytes and rat liver epithelial cells. We observed that pentoxyresorufin O-deethylation activity was well maintained and ethoxyresorufin O-deethylation activity gradually decreased during co-culture time. In addition, we showed that phenobarbital and 3-methylcholanthrene treatments resulted in a significant increase of these activities. Two general patterns of accumulation of liver-specific mRNAs were observed. CYP1A1/2, CYP2B1/2, CYP3A1/2, GST alpha, aldehyde dehydrogenase and epoxide hydrolase mRNAs were maintained at a stable level, whereas CYP2C6 and CYP2E1 mRNAs showed a continuous decline. In addition, we observed a strong increase of CYP1A1/2 (13.6-fold) and GST alpha (3.9-fold) mRNA expression in 3-methylcholanthrene-treated co-cultures and induction of CYP2B1/2 (19-fold), CYP2C6 (10-fold), CYP3A1/2 (11.2-fold), GST alpha (9-fold), aldehyde dehydrogenase (6-fold) and epoxide hydrolase (5-fold) mRNA expression in phenobarbital-treated co-cultures. Furthermore, we demonstrated that liver-specific gene expression was restricted to hepatocytes, with the notable exception of epoxide hydrolase and CYP2E1 which were expressed in both cell types during the co-culture, as shown by the selective recovery of both hepatocytes and rat liver epithelial cells. Finally, to investigate whether co-cultures could be used to study the molecular mechanisms regulating CYP transcription, we performed transfection of hepatocytes, before the establishment of the co-culture, with large CYP2B1 (3.9 kb) or CYP2B2 (4.5 kb) promoter chloramphenicol acetyltransferase constructs or with a construct containing a 163-bp DNA sequence element reported to confer phenobarbital responsiveness. A 2-3-fold increase over the basal level of chloramphenicol acetyltransferase activity was observed in phenobarbital-treated co-cultures transfected with the phenobarbital-responsive element construct, although phenobarbital had no effect on large CYP2B1 or CYP2B2 promoter fragments. Our results demonstrate that the co-culture system provides a good tool for studying drug metabolism, and shows promise as a new tool for analysing transcriptional regulation under the influence of xenobiotics within primary hepatocytes.
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PMID:Regulation of the major detoxication functions by phenobarbital and 3-methylcholanthrene in co-cultures of rat hepatocytes and liver epithelial cells. 906 51

A panel of HepG2-derived cell lines (CAT-Tox [L] assay, Xenometrix), harboring stress genes consisting of a sequence for chloramphenicol acetyltransferase (CAT) under the transcriptional regulation from mammalian promoters and response elements, was exposed for 18-24 hr to aqueous suspensions of urban dusts (SRM-1648, SRM-1649, EHC-93) or PM2.5 particles (particulate matter < 2.5 micron). Expression of CAT protein was measured by enzyme-linked immunosorbent assay. Induction of the CAT genes was verified with benzo[a]pyrene (CYP1A1, cytochrome P450 1A1 promoter; GSTYa, glutathione transferase subunit Ya promoter; XRE, xenobiotic response element), cadmium sulfate, and copper sulfate (HMTIIa, metallothionein IIa promoter; HSP70, heat shock protein 70 promoter). The urban dust suspensions were active on CYP1A1, GSTYa, and XRE cell lines. SRM-1648 and SRM-1649 were twice as potent as EHC-93 per unit mass in inducing the xenobiotic-dependent responses, which correlated with contents in polycyclic aromatic hydrocarbons. These three reference particles, as well as six PM2.5 preparations collected on hi-vol filters in the Great Lakes basin, were also found to induce HMTIIa and HSP70, the magnitude of the responses correlating closely with the amount of soluble copper in the particulate preparations. The results indicate that bioavailable chemical species in the unfractionated particles can directly and quantitatively induce xenobiotic, metal, and stress-dependent responses in a target cell model, resulting in patterns of gene induction consistent with the chemical compositions of the environmental materials. We propose that cell culture models could be helpful for toxicodynamic inferences in adjunct to environmental monitoring and exposure assessments.
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PMID:Regulation of promoter-CAT stress genes in HepG2 cells by suspensions of particles from ambient air. 932 24

The effect of ultraviolet (UV) B irradiation on pi class glutathione transferase (GST-P) gene expression was examined in cultured rat keratinocytes. Immunoblotting demonstrated GST-P to be the major GST form in the cells, and it was significantly decreased following irradiation. Northern blot analysis revealed that the mRNA decreased to 10-25% of the initial value 24 h after irradiation at a dose of 40 mJ/cm2. No remarkable changes were observed at earlier time points. Hydrogen peroxide treatment enhanced GST-P mRNA expression, with a 70% increase at 250 microM concentration. Alterations in possible trans-acting factors were examined to clarify the mechanism of repression by UV irradiation. c-Jun mRNA was induced 3.5-fold at 4 h after irradiation, but by 24 h fell to a lower level than that observed initially. c-Fos mRNA was increased 10-fold at 1 h but was completely suppressed at 12 and 24 h. Thus, the changes of c-Jun and c-Fos mRNA differed from that of GST-P mRNA. The level of mRNA for silencer factor-B was decreased to less than 10% at 12 h. UV irradiation of cells transfected with the chloramphenicol acetyltransferase (CAT) reporter gene containing enhancer (GPE I) or silencer regions of the GST-P gene did not suppress CAT activity. Although basal expression of the GST-P gene was mainly dependent on GPE I, altered expression of c-jun, c-fos and other genes coding for factors possibly trans-acting on GPE I did not appear to be responsible for the decreased GST-P mRNA levels.
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PMID:Decrease in class pi glutathione transferase mRNA levels by ultraviolet irradiation of cultured rat keratinocytes. 943 81

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