Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
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.
 ...
PMID:Evolutionary distinct mechanisms regulate apolipoprotein A-I gene expression: differences between avian and mammalian apoA-I gene transcription control regions. 151 10

In this paper, we examine the mechanisms that regulate the expression of the heavy (H) ferritin subunit in the colon carcinoma Caco-2 cell line allowed to differentiate spontaneously in vitro. The differentiation process of these cells in continuous culture is accompanied by an accumulation of the mRNA coding for the apoferritin H chain. The analysis of Caco-2 subclones stably transfected with an H-chain promoter-chloramphenicol acetyltransferase (CAT) construct revealed that the mRNA increase is paralleled by an enhanced transcription of the H gene, driven by the -100 to +4 region of the H promoter. The H gene transcriptional activation seems to be a specific feature of differentiated Caco-2 cells, since the activity of other promoters did not change upon differentiation. The -100 to +4 region of the H promoter binds a transcription factor called Bbf (B-box binding factor); electrophoretic-mobility-shift-assay analyses showed that the retarded complex due to Bbf-H promoter interaction is significantly increased in the differentiated cells. We propose that the activation of H-ferritin gene expression may be associated with the establishment of a differentiated phenotype in Caco-2 cells, and that the H-ferritin gene transcriptional up-regulation is accompanied by a modification in the activity of the transcription factor Bbf.
 ...
PMID:Transcriptional activation of the H-ferritin gene in differentiated Caco-2 cells parallels a change in the activity of the nuclear factor Bbf. 748 31

The possibility that appropriately designed chemotherapy could act selectively against p53-defective tumor cells was explored in MCF-7 human breast cancer cells. These cells were chosen because they have normal p53 function but are representative of a tumor cell type that does not readily undergo p53-dependent apoptosis. Two sublines (MCF-7/E6 and MCF-7/mu-p53) were established in which p53 function was disrupted by transfection with either the human papillomavirus type-16 E6 gene or a dominant-negative mutant p53 gene. p53 function in MCF-7/E6 and MCF-7/mu-p53 cells was defective relative to control cells in that there were no increases in p53 or p21Waf1/Cip1 protein levels and no G1 arrest following exposure to ionizing radiation. Survival assays showed that p53 disruption sensitized MCF-7 cells to cisplatin (CDDP) but not to several other DNA-damaging agents. CDDP sensitization was not limited to MCF-7 cells since p53 disruption in human colon carcinoma RKO cells also enhanced sensitivity to CDDP. Contrary to the other DNA-damaging agents tested, CDDP-induced DNA lesions are repaired extensively by nucleotide excision, and in agreement with a defect in this process, MCF-7/E6 and MCF-7/mu-p53 cells exhibited a reduced ability to repair a CDDP-damaged chloramphenicol acetyltransferase-reporter plasmid transfected into the cells. Therefore, we attributed the increased CDDP sensitivity of MCF-7 cells with disrupted p53 to defects in G1 checkpoint control, nucleotide excision repair, or both. The G2 checkpoint inhibitor pentoxifylline exhibited synergism with CDDP in killing MCF-7/E6 cells but did not affect sensitivity of the control cells. Moreover, pentoxifylline inhibited G2 checkpoint function to a greater extent in MCF-7/E6 than in the parental cells. These results suggested that, in the absence of p53 function, cancer cells are more vulnerable to G2 checkpoint abrogators. Our results show that a combination of CDDP and pentoxifylline is capable of synergistic and preferential killing of p53-defective tumor cells that do not readily undergo apoptosis.
 ...
PMID:Disruption of p53 function sensitizes breast cancer MCF-7 cells to cisplatin and pentoxifylline. 771 69

Basal promoter activities of various lentiviral long terminal repeats (LTRs) in a human colon carcinoma cell line (SW480 cells) and a feline renal cell line (CRFK cells) were examined by the chloramphenicol acetyltransferase (CAT) assay using the LTR-CAT reporter plasmids. In SW480 cells, the basal promoter activities induced by LTRs of visna virus, caprine arthritis-encephalitis virus (CAEV), and simian immunodeficiency virus (SIVAGM) were moderate, and those induced by LTRs of human immunodeficiency virus (HIV) type 1 (HIV-1) and HIV type 2 (HIV-2) were low. However, the activity induced by the LTR of feline immunodeficiency virus (FIV) was extremely low. In CRFK cells, the basal promoter activities induced by LTRs of visna virus, CAEV and SIVAGM were relatively high, and those induced by LTRs of HIV-1, HIV-2 and FIV were moderate. From these data, although the structure of the LTR of FIV is reported to be similar to that of visna virus and CAEV, the function of the LTR of FIV is rather quite different from that of the LTR of these viruses.
 ...
PMID:Comparative functional analysis of the various lentivirus long terminal repeats in human colon carcinoma cell line (SW480 cells) and feline renal cell line (CRFK cells). 786 91

We have constructed a DNA plasmid encoding the full length complementary DNA for human carcinoembryonic antigen (CEA) driven by the cytomegalovirus early promoter/enhancer (plasmid DNA encoding human CEA) and demonstrated that this plasmid can function as a polynucleotide vaccine. This polynucleotide vaccine induced humoral and/or cellular immune responses specific for human CEA in all 5 immunized mice. Lymphoblastic transformation data with the use of enriched T-cell populations detected the presence of CEA-specific memory T-cells in 3 of 5 mice. Lymphocytes from 2 of 5 mice had interleukin 2/interleukin 4 release in response to CEA. CEA specificity was confirmed by the absence of reactivity to a control antigen and lack of CEA reactivity among mice vaccinated with a control plasmid encoding chloramphenicol acetyltransferase. Four of 5 mice vaccinated with plasmid DNA encoding human CEA demonstrated anti-CEA antibody responses. This immune response compared favorably with a positive control group of mice immunized with vaccinia-CEA by a dose and schedule previously shown to induce immunoprotection and therapy against a human CEA expressing syngeneic murine colon carcinoma model. Studies are ongoing to establish the construct, dose, and schedule to elicit optimal CEA-specific immune response as well as immunoprotection and therapy against human CEA expressing syngeneic murine adenocarcinoma models.
 ...
PMID:Immune response to a carcinoembryonic antigen polynucleotide vaccine. 811

We have investigated a mechanism of the regulation of mucin core polypeptide (MUC1) gene expression, which is induced by a soluble stimulatory factor, in KM12C human colon carcinoma cells. Conditioned media from normal human colon tissues elevated the level of expression of MUC1 mRNA. Transcriptional activation of the MUC1 gene was analyzed by transient expression of MUC1-CAT reporter plasmids containing the 5'-flanking sequence of the MUC1 gene fused to the bacterial chloramphenicol acetyltransferase (CAT) gene. A region between base pairs -531 and -520 of the 5'-flanking sequence of the MUC1 gene was sufficient for the induction of CAT activity by normal colon conditioned medium (NCCM). Mutagenesis of 3 base pairs within the region corresponding to sequence -531 to -517 from ACAGGGAGCGGTTAG to ACAGGGAGATTTTAG substantially decreased the induction of CAT activity by NCCM. Nuclear extracts from untreated or NCCM-treated KM12C cells were tested for their interaction with 32P-labeled oligonucleotides corresponding to this sequence. A specifically retarded band was identified after electrophoretic analysis. The quantity or mobility of this band was not changed by NCCM treatment. When an oligonucleotide with three point mutations was used as a competitor, the retarded band remained at the same position. This element (positions -531 to -520), which we call the responsive mucin element, does not contain any sequence that corresponds to previously described cis-acting elements. A protein component complexed with this sequence was identified with a molecular mass of approximately 70 kDa by SDS-polyacrylamide gel electrophoresis.
 ...
PMID:Transcriptional regulation of the MUC1 mucin gene in colon carcinoma cells by a soluble factor. Identification of a regulatory element. 819 40

To investigate multidrug-resistance gene (MDR1) promoter efficacy and drug inducibility in cells with different multidrug-resistance phenotypes, multidrug-resistant HCT15 and drug-sensitive KM12 human colon carcinoma cell lines were transfected with constructs incorporating the chloramphenicol acetyltransferase (CAT) reporter gene, driven by wild-type and point-mutated MDR1 promoter regions. The basal CAT expression level in HCT15 cells was markedly elevated compared to KM12 cells. CAT induction by vincristine was dose-dependent over a broad concentration range (40-500 ng/ml) in both lines. The induction levels were related to the cells' MDR phenotype, with the multidrug-resistant HCT15 cells showing the greater effect. In both cell types, basal and drug-induced CAT expression were significantly enhanced by the point-mutated promoter regions. The findings support the possible exploitation of the MDR1 promoter for construction of drug-inducible and MDR-cell-targeted expression vectors for use in gene therapy.
 ...
PMID:Vincristine induction of mutant and wild-type human multidrug-resistance promoters is cell-type-specific and dose-dependent. 860 50

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.
 ...
PMID:Aryl hydrocarbon receptor-inducible or constitutive expression of human UDP glucuronosyltransferase UGT1A6. 946 22

The effect of X-irradiation on production of MUC1 was studied with human colon carcinoma HT-29 cells. As evaluated by immunocytochemical staining, the percentages of MUC1-positive cells in cells at 4 days after 6 Gy irradiation and in unirradiated control cells were 52 +/- 3.5% (n = 6) and 26 +/- 2.8% (n = 6), respectively. Flow-cytometric analysis of living cells showed that MUC1 began to rise from day 1, reaching a plateau by day 4 after 6 Gy irradiation. Western blot analysis with monoclonal antibody MY.1E12 against glycosylated MUC1 (mature form) showed dose-dependent increases of two bands (500 and 390 kDa) corresponding to two polymorphic MUC1 alleles. Premature forms of MUC1 (350 and 240 kDa) were detectable with monoclonal antibody HMFG-2 only in irradiated cells, suggesting that new core protein synthesis had been induced. The transcriptional activity of the MUC1 gene was analyzed in terms of transient expression of MUC1-CAT reporter plasmids containing 5'-flanking sequences of the MUC1 gene fused to the bacterial chloramphenicol acetyltransferase (CAT) gene. The results of CAT assay indicate that enhanced expression of MUC1 in irradiated HT-29 cells was due to upregulation of MUC1 transcription, and required the upstream promoter.
 ...
PMID:Increased expression after X-irradiation of MUC1 in cultured human colon carcinoma HT-29 cells. 1076 Jun 92

One of the advantages of viral-directed enzyme prodrug therapy (VDEPT) is its potential for tumor-specific cytotoxicity. However, the viruses used to deliver cDNAs encoding prodrug-activating enzymes transduce normal cells as well as tumor cells, and several approaches to achieve tumor-specific expression of the delivered cDNAs are being investigated. One such approach is to regulate transcription of the prodrug-activating enzyme with a promoter that is preferentially activated by tumor cells. Published data suggest that the most promising transcription factor/promoter/enhancer combinations are those activated by a tumor-specific transcription factor to retain tumor cell specificity but that are equal in strength to nonspecific viral promoters in their ability to up-regulate target cDNAs. This report identifies MYC-responsive, modified ornithine decarboxylase (ODC) promoter/enhancer sequences that up-regulate target protein expression in tumor cells overexpressing either N-MYC or c-MYC protein. The most efficient of the four constructs assessed contained six additional CACGTG MYC binding sites 5' to the endogenous ODC promoter (R6ODC). Reporter assays with this chimeric promoter/enhancer regulating expression of chloramphenicol acetyltransferase demonstrated 50-250-fold more activity in MYC-expressing cells compared with similar assays with promoterless plasmids. The R6ODC regulatory sequence was approximately equivalent to the CMV promoter in inducing expression of the neomycin resistance gene in c-MYC-expressing SW480 and HT-29 colon carcinoma cells and in N-MYC-expressing NB-1691 neuroblastoma cells. The modified ODC promoter may, therefore, be useful in achieving tissue-specific expression of target proteins in tumor cells that overexpress c- or N-MYC.
 ...
PMID:Use of a modified ornithine decarboxylase promoter to achieve efficient c-MYC- or N-MYC-regulated protein expression. 1130 86


1