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)

The 5'-flanking region of the metallothionein (MT) gene LpMT1 of the sea urchin Lytechinus pictus includes three copies of a conserved sequence that includes the metal-responsive element (MRE) consensus core sequence required for heavy metal induction of other MT genes, a GC box, a G box of a putative basal level enhancer element which includes another MRE core element, and a poly(C) tract. A fragment of LpMT1 DNA from nucleotides +31 to -309 fused to a chloramphenicol acetyltransferase reporter gene was inducible with cadmium after injection into L. pictus embryos. This induced activity was greatly reduced in a deletion mutant which retained only 195 base pairs of 5'-flanking sequence, including the proximal pair of MREs and the G box, but excluding the poly(C) tract, GC box, and distal MRE. A potent human hMT-IIA gene promoter is marginally functional in L. pictus embryos. In contrast, the LpMT1 promoter is active in HeLa cells and in embryos of the sea urchin Strongylocentrotus purpuratus. The hMT-IIA gene may lack a cis-acting sequence element required for expression of MT genes in L. pictus embryos. The LpMT1 promoter is a powerful, inducible, promiscuous promoter useful for driving the expression of heterologous genes in sea urchin embryos.
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PMID:Functional analysis of the promoter of a sea urchin metallothionein gene. 129 38

The TAR sequence of the 5' leader of HIV-1 long terminal repeat-directed mRNA was found to be able to bind to and to activate double-stranded RNA-dependent (2'-5')A synthetase. Binding of TAR to the purified synthetase in vitro was abolished by addition of HIV-1 Tat protein, which binds to this sequence with a high affinity. Inhibition of TAR-mediated activation of (2'-5')A synthetase by Tat was prevented in the presence of the Zn2+ and Cd2+ chelators o-phenanthroline and penicillamine, which did not impair TAR-synthetase interaction. Transient expression assays of bacterial chloramphenicol acetyltransferase (CAT) gene in HeLa cells revealed that the levels of both CAT mRNA and CAT protein decreased after treatment of the cells with interferon, if CAT gene was linked to HIV-1 TAR segment. Cotransfection of the cells with a tat sequence containing plasmid rendered CAT gene expression insensible to the action of interferon.
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PMID:Binding of Tat protein to TAR region of human immunodeficiency virus type 1 blocks TAR-mediated activation of (2'-5')oligoadenylate synthetase. 169 53

Sequence similarity between alpha B-crystallin and small heat shock proteins (HSPs) has prompted us to investigate whether alpha B-crystallin expression is induced by heat shock. Indeed, accumulation of alpha B-crystallin was detected immunologically in NIH 3T3 cells after incubation at elevated temperatures and after addition of Cd2+ or sodium arsenite to these cells. Two-dimensional gel electrophoresis revealed identity between alpha B-crystallin from eye lenses and from heat-treated fibroblasts. The promoter of the alpha B-crystallin gene was fused to the bacterial chloramphenicol acetyltransferase gene and was shown to confer heat inducibility on this reporter gene in transient transfection assays. A perfect heat shock element within the promoter region is likely to mediate this response. Small HSPs and alpha B-crystallin were shown to share the following two physical properties: (i) they form supramolecular structures with sedimentation values around 17 S and (ii) they are associated with the nucleus at high temperatures and are localized in the cytoplasm under normal conditions. We conclude that alpha B-crystallin has to be considered a member of the class of small HSPs.
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PMID:Alpha B-crystallin is a small heat shock protein. 202 14

We and others have introduced the use of the lac operator-repressor system as a method for providing inducible gene expression for gene transfer experiments in animal cells (M. C.-T. Hu, and N. Davidson, Cell 48:555-566, 1987; J. Figge, C. Wright, C. J. Collins, T. M. Roberts, and D. M. Livingston, Cell 52:713-722, 1988). To improve the dynamic range of such an inducible system, we have investigated the effects of combining the relief by isopropyl-beta-D-thiogalactoside (IPTG) of negative control by the lac system with positive induction by the natural inducers glucocorticoids and cadmium ion for a system based on the human metallothionein-IIA gene promoter. We used the chloramphenicol acetyltransferase gene as a reporter gene and inserted a lacO sequence into the promoter between the GC box and metal-responsive element 1, between metal-responsive element 1 and the TATA box, or between the TATA box and the transcription start site. Surprisingly, all of these insertions had a significant inhibitory effect on promoter activity even in the absence of repressor. However, with these lacO-containing constructs, the levels of gene expression after induction by glucocorticoid, Cd2+, or both were considerably reduced in cells engineered to express the lac repressor. Derepression by IPTG, coupled with induction by both dexamethasone and Cd2+ ion, then provided a high level of induced expression, i.e., by a factor of approximately 100 over the basal level of expression. However, inserting the lacO sequence well upstream just before the glucocorticoid-responsive element had much smaller effects on expression levels in both repressor-negative and repressor-positive cells. This study describes a new, high-level-inducible promoter system for gene transfer experiments. The observed effects are discussed in terms of current models of the mechanisms by which transcription factors control gene expression.
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PMID:A combination of derepression of the lac operator-repressor system with positive induction by glucocorticoid and metal ions provides a high-level-inducible gene expression system based on the human metallothionein-IIA promoter. 224 53

Rat cell lines were established in which the bacterial chloramphenicol acetyltransferase (CAT) gene under control of the human immunodeficiency virus (HIV) long terminal repeat (LTR) was stably integrated. The cell lines showed a repressed phenotype for CAT expression, but could be induced for it by inhibition of protein synthesis, as well as by heat-shock and chemical inducers of the cellular stress response, such as sodium arsenite, 8-hydroxyquinoline and the heavy metals cadmium and copper. A decameric sequence present in the NF-kB binding sites in the HIV LTR (GGGACTTTCC) resembles the cellular heat-shock core sequence and may therefore be involved in the heat-shock response.
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PMID:Heat-shock induction of the human immunodeficiency virus long terminal repeat. 318 32

The trout metallothionein (MT) genes consist of two members. We describe the structure of the first fish MT (tMT-B) gene which shows an overall resemblance but some remarkable differences with mammalian MT genes. The similarities included (i) tripartite structure of the gene, (ii) conservation of cysteine residues, and (iii) a TATAAA signal and two copies of metal-responsive elements (MREs). The differences consisted of (i) an AT-rich tMT-B promoter compared with highly GC-rich mammalian MT promoters and (ii) a lack of SP1-binding sites in the tMT-B promoter. Functional analysis of the tMT-B 5'-flanking region following fusion with the bacterial chloramphenicol acetyltransferase gene and its transfection into the rainbow trout hepatoma cell line revealed that sequences from positions -600 to +8 are sufficient for regulation by metals. Further deletion analyses of this fragment suggested that a minimum of 100 nucleotides upstream of the transcription initiation site are required for induction by cadmium and zinc. The tMT-B promoter was also functional in the human hepatoblastoma cell line, suggesting that an MT regulatory factor(s) is conserved in phylogenetically distant species like humans and fish.
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PMID:Structure of the rainbow trout metallothionein B gene and characterization of its metal-responsive region. 318 57

The human metallothionein (MT)-IG gene (hMT-IG) is tandemly linked in a head-to-head fashion with the hMT-IF gene. The hMT-IG gene encodes a MT-I polypeptide and has a tripartite structure. The 5'-flanking region of the hMT-IG gene has a TATAA box, four GC motifs, and at least four metal responsive elements. The 3'-untranslated region has a variation of the polyadenylation signal, AATTAA, and the 3'-flanking region a YGTGTTYY RNA processing signal. This gene is expressed in hepatoma-derived cell lines (Hep G2 and Hep3B2) in response to the heavy metals (cadmium, copper, and zinc) but not to the glucocorticoid analogue dexamethasone. In contrast, the lymphoblastoid cell line (Wi-L2) does not express the hMT-IG gene. These results suggest that the hMT-IG gene is regulated differentially and in a cell type-specific manner. Transient expression studies of the chloramphenicol acetyltransferase (CAT) gene under the transcriptional control of either the hMT-IG or hMT-IF promoter in Hep G2 cells has demonstrated that both promoters contain all the necessary cis-acting elements to elicit a similar pattern of heavy metal inducibility. However, the hMT-IG promoter in all instances is five times more active than the hMT-IF promoter. The differences in promoter activity of these genes could possibly be due to inherent differences in their basal level regulatory sequences. The expression of MT-IGcat in transfected Wi-L2 cells demonstrates that the hMT-IG promoter is not cell type-specific.
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PMID:Structure and expression of the human metallothionein-IG gene. Differential promoter activity of two linked metallothionein-I genes in response to heavy metals. 340 43

The expression of the human HSP70 gene is induced by a wide range of physiological stresses, including exposure to heat shock and heavy metals, or under nonstress conditions, such as in response to serum stimulation. We have previously demonstrated that in either case the regulated expression is at the primary level of transcription. To determine whether transcription is mediated through a single or multiple genetic elements, we have dissected the sequences upstream of the transcription start site of the human HSP70 gene by constructing chimeric genes retaining variable amounts of 5' flanking regions fused to the bacterial gene encoding chloramphenicol acetyltransferase. Transcription from the chimeric genes was determined by S1 nuclease analysis of separate stable transfectants. The sequences required for heat shock and cadmium induction lie between -107 and -68. Within this region is the sequence CTGGAATATTCCCG, which is identical in 12/14 positions with the heat shock element of Drosophila heat shock genes, and a separate sequence, CGNCCCGG, which is homologous to the core of the human metallothionein II metal-responsive element. The sequences required for serum-stimulated transcription are distinct from the heat shock element. The sequence CCAAT at -68 is required for high levels of correctly initiated transcripts, and a purine-rich sequence, GAAGGGAAAAG, at -58 is required for serum stimulation. The human HSP70 promoter contains at least two regulatory domains--a distal domain responsive to heat shock or cadmium and a proximal domain responsive to stimulation by serum.
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PMID:Human HSP70 promoter contains at least two distinct regulatory domains. 345 60

We introduced plasmid pCmVCAT containing a chloramphenicol acetyltransferase (CAT) gene, flanked by the cauliflower mosaic virus 35S promoter and nopaline synthase polyadenylation sequences, into Chlamydomonas reinhardtii by electroporation; chloramphenicol (CAM) resistance was used for selection. Several mutants with aberrant response to cadmium (Cd) toxicity were obtained by screening CAM resistant transformants. Southern blot analysis showed random integration of pCmVCAT sequence into the nuclear genome. Expression of CAT gene was confirmed by the detection of CAT gene transcript in Northern blot analysis and the detection of CAT enzyme by ELISA assay. This study demonstrated the feasibility of transforming Chlamydomonas reinhardtii with heterologous DNA by electroporation, and the expression of heterologous gene, in this alga.
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PMID:Insertion mutagenesis of Chlamydomonas reinhardtii by electroporation and heterologous DNA. 758 Sep 98

A 268-base pair 5' distal fragment, SX2, which mediates basal level and inducer-dependent activation of the mouse heme oxygenase-1 gene, contains two activator protein-1 (AP-1) binding sites (Alam, J., and Zhining, D. (1992) J. Biol. Chem. 267, 21894-21900). Mutation of both AP-1 binding elements diminishes (by 50-70%), but does not abolish, the enhancer activity of SX2 in transient expression assays, suggesting that other sequences contribute to enhancer function. Directly upstream of the AP-1 binding sites are two copies of a sequence motif, TGAGGAAAT, which resemble elements found in cellular and viral genes that are known to interact with the CCAAT/enhancer-binding protein (C/EBP) family of transcription factors. These SX2 sequences bind specifically to liver-enriched, heat-stable nuclear proteins and confer C/EBP alpha-dependent transactivation of the heterologous chloramphenicol acetyltransferase (CAT) gene. Site-directed mutagenesis of these 9-base pair elements abolishes protein binding and transactivation, establishing these sequences as functional C/EBP binding sites. Stably transfected SX2/CAT fusion genes are induced between 37- and 44-fold in mouse hepatoma, Hepa, cells and between 52- and 111-fold in mouse fibroblast L929 cells in response to CdCl2 treatment. Subfragments of SX2 lacking the AP-1 binding elements do not mediate cadmium-dependent activation of the CAT gene, whereas subfragments containing the AP-1 binding elements, but lacking the C/EBP binding sites, exhibit only partial transcriptional activity. Site-directed mutagenesis of one or more of the C/EBP and AP-1 binding sites indicates that each of these elements is required for optimal activity of the SX2 enhancer fragment. The AP-1 binding elements, however, appear to be more important for induction as constructs containing multiple copies of either of the AP-1 binding elements, but not the C/EBP binding sequences, are readily activated by CdCl2. Treatment of Hepa cells with cadmium or heme does not alter the nuclear concentration of AP-1 or C/EBP binding activity.
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PMID:Multiple elements within the 5' distal enhancer of the mouse heme oxygenase-1 gene mediate induction by heavy metals. 792 91


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