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 mammals, the apolipoprotein (apo) A-I gene is expressed predominantly in liver and intestine, while in avian species it is expressed in all tissues. Although liver and intestine are the major sites of chicken apoA-I mRNA synthesis, there are appreciable amounts of apoA-I mRNA in kidney, ovary/testes, brain, lung, skeletal, and heart muscle. In this study, the nucleotide sequences of the chicken apoA-I gene and its 5' flanking region, as well as the sequences involved in the expression of this gene, have been determined. The gene spans 1.5 kilobases and contains 4 exons and 3 introns, closely resembling the mammalian apoA-I gene. To determine the sequences involved in the expression of the chicken apoA-I gene, plasmid constructs containing serial deletions of the 5' flanking region of the chicken apoA-I gene fused to the bacterial chloramphenicol acetyltransferase (CAT) gene were transfected in human hepatoma (HepG2), colon carcinoma (Caco2), epithelial (Hela), mouse embryonal fibroblast (NIH3T3) cells, and quail myoblasts (QMLA29). The shortest deletion construct, containing 60 bp of the 5' upstream region, was sufficient for maximal transcriptional activity in all cell lines tested. This region contains a short sequence (nucleotides -60 to -54) that is highly conserved in birds and mammals, and an Sp1 binding site. Although the sequence between nucleotides -232 and -101 of the 5' region of the chicken apoA-I gene is partially homologous to the hepatic cell-specific enhancer of the mammalian apoA-I gene (located between nucleotides -222 and -110 upstream of the human apoA-I gene transcription start site), this chicken sequence is transcriptionally inactive in HepG2 cells. These results suggest that differences in the cis-acting regulatory elements of the apoA-I gene play a fundamental role in determining the differences in the tissue-specific expression of this gene in avian and mammalian species.
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PMID:Evolutionary distinct mechanisms regulate apolipoprotein A-I gene expression: differences between avian and mammalian apoA-I gene transcription control regions. 151 10

We have isolated and characterized a 2.5-kilobase pairs genomic DNA fragment which includes the 5'-flanking region and the first and second exons of the human apolipoprotein (apo) A-I gene. The major transcriptional start site was determined by primer extension analysis and is 235 base pairs (bp) upstream from the AUG translational start codon in liver and 234 bp upstream in the intestine. TATA box-like and CAT box-like sequences and two GC box sequences are present in the intestine 30, 108, 220, and 440 bp upstream, respectively, from the transcriptional start site. Fragments of 570 bp (-487 to +71) and 2.15 kilobase pairs (-2067 to +99) containing the 5'-flanking region of the apoA-I gene were fused upstream to the bacterial chloramphenicol acetyltransferase (CAT) gene. These constructs, designated pA-I(0.6)CAT and pA-I(2.2)CAT, respectively, were introduced into human oral epithelial cells (KB), mouse NIH 3T3 cells, Chinese hamster ovary (CHO) cells, human hepatoma cells (Hep G2), human duodenal epithelial cells (Hutu 80), and human colonic epithelial cells (Caco-2) by calcium phosphate coprecipitation. When compared with control vectors, highly efficient CAT expression of both the pA-I(0.6)CAT and pA-I(2.2)CAT constructs were observed only in cells derived from the liver (Hep G2) and intestine (Caco-2), which is consistent with the tissue specificity of expression of the native gene. Analysis of deletion mutants of the human apoA-I 5'-flanking region revealed that: 1) the region from -250 to -199 bp, from -487 to -413 bp, and -1021 to -691 bp upstream from the transcriptional start site contain sequences required for maximum gene expression; and 2) the regions from -2067 to -1476 bp and -199 to -80 bp contain the sequences required for tissue-specific repression of apoA-I gene expression in non-apoA-I producing cells.
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PMID:Tissue-specific expression of apolipoprotein A-I (ApoA-I) is regulated by the 5'-flanking region of the human ApoA-I gene. 314 80

Earlier studies from our laboratory indicated that apolipoprotein A-I (Apo A-I) stimulates the acute release of human placental lactogen (hPL) from trophoblast cells in culture. We have now demonstrated that Apo A-I also causes a secondary increase in hPL release, beginning about 6 h after exposure to Apo A-I, that is blocked by cycloheximide and actinomycin D. Apo A-I also stimulated a dose-dependent increase in hPL promoter activity in JAR cells transfected with a 1.1-kilobase (-1078/2) fragment of the hPL3 promoter coupled to a chloramphenicol acetyltransferase (CAT) reporter gene. Maximal stimulation, 5.2-fold above basal levels, occurred at an Apo A-I concentration of 1.5 mg/ml, which is within the physiological concentration of Apo A-I during pregnancy. 37pA, a synthetic amphipathic peptide that mimics the secondary structure of Apo A-I and stimulates the synthesis and release of hPL, also stimulated a dose-dependent increase in CAT activity, with maximal stimulation comparable to that caused by Apo A-I. In addition, Apo A-I stimulated a modest increase in CAT activity in BeWo choriocarcinoma cells, Chinese hamster ovary cells, and HeLa cells. However, the maximal stimulation of hPL promoter activity in the Chinese hamster ovary and HeLa cells (approximately 2.5-fold above basal levels) was less than that in choriocarcinoma cells, suggesting that trophoblast cell nuclear factors may be necessary for maximal expression of the promoter in response to Apo A-I. Taken together, these results indicate that Apo A-I stimulates hPL gene expression, and that DNA elements in the first 1.1 kilobase of the promoter are sufficient for transactivation by Apo A-I.
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PMID:Apolipoprotein A-I stimulates placental lactogen expression by human trophoblast cells. 758 8

Fibrates have been reported to modulate plasma high density lipoprotein cholesterol and apolipoprotein (apo) A-I concentrations. Therefore, the molecular mechanisms underlying the regulation of human apoA-I gene expression by fibrates was investigated. Fenofibrate reduced the expression of a reporter gene driven by the DNA sequences between -192 and +91 (BC-P-chloramphenicol acetyltransferase; CAT) relative to the apoA-I gene transcription start site approximately 3-fold. The sequences involved in the down-regulation of apoA-I gene transcription by fenofibrate were localized between -41 and +91 (P-CAT) relative to the transcription start site. The reduction of the expression of BC-P-CAT was dose-dependent and maximal at 500 microM (20 +/- 7%). Different peroxisome proliferators showed different levels of repression varying from 39 +/- 4% for fenofibrate, 43 +/- 5% for tetradecylthioacetic acid, 48 +/- 4% for bezafibrate, 54 +/- 2% for 5,8,11,14-eicotetraynoic acid, 76 +/- 2% for ciprofibrate, whereas Wy 14643 only marginally inhibited the expression of BC-P-CAT. By contrast, inclusion of sequences between -256 and -192 (ABC-P-CAT) attenuated the repression by fenofibrate. Furthermore, the apoA-IA site (-214 to -192; Awt-P-CAT) could counteract the repression of P-CAT by fenofibrate in the presence of cotransfected mPPAR alpha (peroxisome proliferator-activated receptor). In addition, the acyl-CoA oxidase-peroxisome proliferator response element (PPRE) could substitute the wild-type A-site in blocking the fenofibrate-induced reduction of the apoA-I promoter by mPPAR alpha. The protective effect of PPAR on fenofibrate induced inhibition of apoA-I expression was abolished after mutation of the direct repeat in the A site (Am-P-CAT). Consistent with these functional data only the wild-type, but not the mutated A site bound PPAR/retinoic X receptor heterodimers in gel shift assays. These data suggest that certain peroxisome proliferators can reduce the expression of the apoA-I promoter in a PPAR-independent fashion, through modulation of factors interacting with sequences localized between -41 and +91 of the apoA-I gene transcription initiation site. This inhibitory effect can be overcome when PPAR interacts with a functional PPRE, such as the apoA-I A site or the acyl-CoA oxidase-PPRE.
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PMID:Negative regulation of the human apolipoprotein A-I promoter by fibrates can be attenuated by the interaction of the peroxisome proliferator-activated receptor with its response element. 798 38

Studies were designed to examine the regulation of apolipoprotein (apo) A-I gene expression in Cu-depleted Hep G2 cells. The cupruretic chelator N,N'-bis(2-aminoethyl)-1,3-propanediamine 4 HCl (2,3,2-tetramine or TETA) was used to maintain a 77% reduction in cellular Cu in Hep G2 cells. After two passages of TETA treatment, the relative abundance of apoA-I mRNA was elevated 52%. In TETA-treated cells, the rate of apoA-I mRNA decay measured by an actinomycin D chase study was accelerated 108%, and the synthesis of apoA-I mRNA determined by a nuclear runoff assay was enhanced 2.5-fold in TETA-treated cells. All of those changes could be reverted toward the control values with Cu supplementation for only 2 days. In transient transfection assays, a 26.7% increase in chloramphenicol O-acetyltransferase (CAT) activity for the reporter construct -256AI-CAT was observed in the treated cells. However, the ability of apoA-I regulatory protein 1 (ARP-1) to repress the CAT activity was not affected by the depressed Cu status. In addition, gel retardation experiments demonstrated that Cu depletion enhanced the binding of hepatocyte nuclear factor 4 (HNF-4) and other undefined nuclear factors to oligonucleotides containing site A, one of three regulatory sites of the apoA-I gene promoter. Moreover, the relative abundance of HNF-4 mRNA was increased 58% in the Cu-depleted cells. Thus the observed increase in apoA-I gene transcription may be mediated mostly by an elevated level of the regulatory factor, HNF-4. In summary, the present findings established the mechanism by which a depressed cellular Cu status can enhance apoA-I mRNA production and subsequently increase apoA-I synthesis.
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PMID:Regulation of apolipoprotein A-I gene expression in Hep G2 cells depleted of Cu by cupruretic tetramine. 935 82

In Escherichia coli mRNA, the arginine codons AGA/AGG and the isoleucine codon AUA are rarely used with frequencies of about 0.35% and 0.41%, respectively. Six genes with a different number of these codons were expressed in an E. coli in vitro coupled transcription/translation system, which contained either tRNA prepared from E. coli cells carrying a plasmid with argU and ileX genes encoding rare tRNAs (tRNA(arg)(AGA/AGG) and tRNA(ile)(AUA)), designated codon-plus tRNA, or normal tRNA from cells lacking the plasmid. Genes having a low number of the rare codons, such as genes encoding chloramphenicol acetyltransferase and anti-gp120 single-chain Fv (artificially constructed to remove rare codons), were expressed at similar levels using with both tRNA preparations. On the other hand, the use of codon-plus tRNA increased the expression levels of genes having a relatively large number of the rare codons, including genes encoding archaeal proteins, green fluorescent protein of jelly fish origin, and a single-chain Fv of mouse origin, by about 20% higher than that using normal tRNA.
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PMID:Dosage effect of minor arginyl- and isoleucyl-tRNAs on protein synthesis in an Escherichia coli in vitro coupled transcription/translation system. 1623 46