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 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

In recent studies we have identified PC2 and PC3, members of a family of serine proteases that are related structurally to subtilisin, and have provided evidence that these are involved in the tissue-specific processing of prohormones and neuropeptides. PC2 is expressed at high levels in the islets of Langerhans, where it participates in the processing of proinsulin to insulin (S.P.S. and D.F.S., unpublished data). To evaluate the regulated expression of the human PC2 (hPC2) gene we have analyzed its structure and characterized its promoter. A map of the gene was constructed by using 11 clones isolated from two human genomic DNA libraries. The gene spans greater than 130 kilobase pairs and consists of 12 exons. Comparison with the structure of the gene encoding human furin, another member of this superfamily, revealed a high degree of conservation of exon-intron junctions. The hPC2 gene was localized to chromosome 20, band p11.2. The 5' flanking region of the hPC2 gene is very G+C-rich and contains six potential Sp1 binding sites but no TATA or CAAT box. Expression of chloramphenicol acetyltransferase reporter fusions containing the putative promoter region was observed to occur in beta TC-3 mouse insulinoma cells but not in HepG2 human hepatoma cells, consistent with the known tissue-specific pattern of expression of the hPC2 gene. Analysis of the level of chloramphenicol acetyltransferase activity with several deletion mutants identified the region from -1100 to -539 from the translation start site as essential for hPC2 promoter activity.
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PMID:Identification and analysis of the gene encoding human PC2, a prohormone convertase expressed in neuroendocrine tissues. 159 2

Plasminogen activator inhibitor-1 (PAI-1) is a serine protease inhibitor that inhibits both tissue-type and urokinase-type plasminogen activators. Expression of PAI-1 is regulated by growth factors, cytokines, and hormones. To determine the molecular mechanisms involved in the basal expression of the rat PAI-1 gene, we have analyzed the cis-acting sequences and the trans-acting factors involved in the transcription of this gene in the HTC rat hepatoma cell line. DNase I protection analyses revealed eight regions within the first 764 base pairs of 5'-flanking sequence that interact specifically with HTC cell nuclear proteins. The proteins that bind to five of the eight footprinted sites were identified as PEA3-, Sp1-, and CTF/NF-1-like proteins using competition electrophoretic mobility shift assays. The expression of fusion genes containing progressive 5' deletions of the rat PAI-1 promoter linked to the chloramphenicol acetyltransferase reporter gene were analyzed in transient transfection experiments in HTC cells. These studies demonstrated the Sp1 and CTF/NF-1 sites to be important for transcriptional activation. Two of the footprinted sites contain the sequence 5'-TTTGn(n)TCAAT-3' and were shown in competition electrophoretic mobility shift assays to bind the same or related protein(s). Sequences containing these sites, from -764 to -628 base pairs, and from -266 to -188 base pairs, were identified in functional studies as repressor elements of transcription.
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PMID:Regulatory sequences and protein-binding sites involved in the expression of the rat plasminogen activator inhibitor-1 gene. 160 87

We investigated a common polymorphism in the human apolipoprotein A-I gene promoter at a position 76 bp upstream of the transcriptional start site. 54 human subjects, whose apoAI production rates had been determined by apoAI turnover studies, were genotyped at this polymorphic position by a novel technique using polymerase chain reaction followed by primer extension. 35 subjects were homozygous for a guanosine (G) at this locus and 19 were heterozygous with a guanosine and adenosine (A). The apoAI production rates were significantly lower (by 11%) in the G/A heterozygotes than in the G homozygotes (P = 0.025). In spite of the apparent effect of this apoAI gene promoter polymorphism on the apoAI production rate, there was no effect on HDL cholesterol or apoAI levels. To investigate whether the observed difference in apoAI production rates was related to differential gene expression of the two alleles, promoters containing either allele were linked to the reporter gene chloramphenicol acetyltransferase, and relative promoter efficiencies were determined after transfection into the human HepG2 hepatoma cell line. The A allele expressed only 68% +/- 5% as well as the G allele, a result consistent with the in vivo apoAI production rate data.
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PMID:Polymorphism in the human apolipoprotein A-I gene promoter region. Association of the minor allele with decreased production rate in vivo and promoter activity in vitro. 160 89

The degradation of ornithine decarboxylase (ODC) is stimulated by polyamines in a protein synthesis-dependent manner. It has been suggested that antizyme, an ODC-inhibiting protein induced by polyamines, is involved in the process of polyamine-stimulated ODC decay. In this study, we investigated the direct effect of antizyme on ODC decay in hepatoma tissue culture (HTC) cells. A truncated rat antizyme cDNA, Z1, was inserted into an expression vector at a site under the control of a glucocorticoid-inducible promoter and transfected into HTC cells. In the transfected cells dexamethasone increased the amount of Z1 mRNA and induced active antizyme in the absence of exogenous polyamines. When dexamethasone was added to cells with a high level of ODC, rapid decays of ODC activity and protein were elicited after a lag time. Cycloheximide abolished the effect of dexamethasone. These effects of dexamethasone were not observed in control HTC cells transfected with the chloramphenicol acetyltransferase gene. This study indicated that, once induced, antizyme stimulated ODC degradation independently of polyamines and strongly supported our previous hypothesis that the ODC decay-accelerating action of polyamines is mediated by antizyme.
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PMID:Destabilization of ornithine decarboxylase by transfected antizyme gene expression in hepatoma tissue culture cells. 161 15

The human aldolase A gene is transcribed from three different promoters, which are all clustered within a 1.6 kbp DNA domain. Two of these, PN and PH, are ubiquitous and seem to be co-regulated in most tissues while the third one, PM, is specific to adult skeletal muscle. We investigated the sequences involved in the ubiquitous activity of the PN and PH promoters of the human aldolase A gene. Deletion analysis, performed by transient expression assays of chloramphenicol acetyltransferase reporter genes in human HepG2 hepatoma cells, indicated that PH activity results from the interaction of an upstream activating region with two distinct core promoters. The upstream activating region was able to stimulate transcription from the HSV tk promoter as efficiently as the SV40 enhancer in all cell types tested. It appears, therefore, to be a strong ubiquitous enhancer. DNAsel footprinting revealed protections covering sequences scattered along the enhancer, including Sp1 and AP1 motifs. Importantly, we found that this enhancer was also necessary to activity of the other ubiquitous promoter of the aldolase A gene, PN. These studies demonstrate that expression of the human aldolase A gene is mediated by a complex interplay of enhancer and promoter elements.
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PMID:A ubiquitous enhancer shared by two promoters in the human aldolase A gene. 165 79

Interleukin-6 is a pleiotropic cytokine that has a major role in the coordination of the hepatic acute phase response. In order to more fully understand this role, we have examined the interleukin-6 induction of T kininogen, a cysteine protease inhibitor and a major acute phase reactant in the rat. Using deletional analysis and site-directed mutagenesis of T kininogen-chloramphenicol acetyltransferase fusion constructs transfected into HepG2 hepatoma cells, we have identified two similar interleukin-6 response elements within 250 base pairs of the transcription start site. These two response elements are functionally interdependent. The sequences of these two elements match the consensus sequence for the previously described Type B interleukin-6 response element. Interleukin-6 signal transduction via two Type B elements has not been observed previously in vivo. A DNA fragment encompassing these response elements forms the same protein complex with nuclear extracts from both untreated and interleukin-6-treated cells.
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PMID:Identification of sequences mediating interleukin-6 induction of a rat T kininogen gene. 165 51

The ability of a retinoic acid (RA) response element (RARE) in the phosphoenolpyruvate carboxykinase (PEPCK) gene promoter to mediate effects of either RA or thyroid hormone (T3) on gene expression was studied. Fusion gene constructs consisting of PEPCK promoter sequences ligated to the chloramphenicol acetyltransferase (CAT) reporter gene were used for this analysis. While T3 induced CAT expression to a small degree (about twofold) when such constructs were transiently transfected into H4IIE rat hepatoma cells, along with an expression vector encoding the alpha subtype of the T3 receptor (TR), this effect was mediated by promoter sequences distinct from the PEPCK RARE. Although TRs were capable of binding the PEPCK RARE in the form of putative monomers, dimers, and heterodimers with RA receptors (RARs), this element failed to mediate any positive effect of T3 on gene expression. In contrast, the PEPCK RARE mediated six- to eightfold induction of CAT expression by RA. When TRs were coexpressed along with RARs in transfected H4IIE cells, this RA induction was substantially blunted in a T3-independent manner. This inhibitory effect may be due to the binding of nonfunctional TRs or TR-RAR heterodimers to the PEPCK RARE. A model is proposed to explain the previously observed in vivo effects of T3 on PEPCK gene expression.
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PMID:Specificity of a retinoic acid response element in the phosphoenolpyruvate carboxykinase gene promoter: consequences of both retinoic acid and thyroid hormone receptor binding. 194 93

We investigated the 5'-flanking region of the rat angiotensinogen gene to define the DNA elements conferring inducibility by glucocorticoids and estrogens. Two putative glucocorticoid-responsive elements (GREs) based on sequence comparison were identified. Here we report the functional importance of these sequences. We constructed several deletion mutants of the 5'-region in front of the bacterial reporter gene for chloramphenicol acetyltransferase (CAT). The angiotensinogen-CAT-reporter plasmids (pRagCAT) were transiently transfected into the rat hepatoma cells FTO 2B and Fe 33. All pRagCAT constructs in which the 5'-region contained at least one of the two GRE consensus sequences were stimulated by dexamethasone. On the other hand, deletion mutants containing no GRE sequences were not inducible with dexamethasone. In additional experiments, the transcriptional functions of the two putative GREs were assessed by cloning synthetic oligonucleotides encompassing the GRE sequences directly in front of the heterologous herpes simplex virus thymidine-kinase promoter. Our results showed that each synthetic GRE was capable of stimulating the heterologous TK promoter after administration of dexamethasone and that both GREs together act synergistically. We also investigated the transcriptional control of angiotensinogen by estrogen. Although no estrogen-responsive element consensus sequences were detectable by sequence comparison, we did identify sequences between -60 to -92 which conferred estrogen inducibility to the rat angiotensinogen gene. In this region, a so-called half-palindromic estrogen-responsive element is localized at nucleotides -87 to -91.
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PMID:Glucocorticoid- and estrogen-responsive elements in the 5'-flanking region of the rat angiotensinogen gene. 166 57

Two gamma-glutamyl transpeptidase mRNAs (mRNAI and mRNAII), with alternate 5'-untranslated regions, are expressed in the rat kidney. Oligonucleotides were designed based upon these two alternate 5' sequences and used as primers to amplify GGT genomic DNA sequences. The genomic organization of the mRNAI and mRNAII 5'-untranslated sequences reveals that the mRNAs are encoded from two separate promoters which are 2.1 kbp apart on the single GGT gene. A 2775 base pair genomic sequence, which contains the proximal GGT promoter, was cloned from two overlapping amplified fragments. S1 mapping analysis shows that the kidney GGT mRNAI is transcribed from several start sites on this promoter which displays neither a classical TATA box nor Sp1 binding sites. Chimeric plasmids, including the GGT promoter region for mRNAI, associated with the chloramphenicol acetyltransferase (CAT) reporter gene, were transiently expressed in a kidney (LLCPK) and in a hepatoma (HTC) cell line. A sequence extending 308 bases upstream from the major GGT mRNAI start site drives a promoter activity which is 5-fold higher in LLCPK than in HTC cells and is sufficient to confer cell specificity to the GGT proximal promoter.
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PMID:Organization of the 5' end of the rat gamma-glutamyl transpeptidase gene: structure of a promoter active in the kidney. 167 56


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