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)

Basal expression of a chimeric gene (pMHO4CAT) consisting of approximately 7 kilobase pairs (kbp) of the 5'-flanking region of the mouse heme oxygenase-1 (HO-1) gene fused to the bacterial chloramphenicol acetyltransferase gene is 2- to 10-fold greater than that of an analogous construct containing only 1287 bp of the 5'-flanking region (pMHO1CAT) in transiently transfected cultured cells. The enhancer activity has been localized to a 268-base pair (bp) fragment positioned approximately 4 kilobase pairs upstream of the transcription initiation site. This fragment contains two high affinity protein binding sites, regions A and B, as determined by DNase I protection assays using nuclear protein extracts from rat C6 glioma cells. Both sites include core sequence elements, TGAGTCA (region A) and TGTGTCA (region B), that resemble the consensus binding site, TGA(G/C)TCA, of the Jun/Fos (AP-1) family of transcription factors. Purified, bacterially expressed AP-1 (c-Jun homodimer) specifically binds to both elements, exhibiting greater affinity for the region A motif. The expression of pMHO4CAT, but not of pMHO1CAT, is stimulated by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), and the 268-bp enhancer fragment confers TPA inducibility and c-Jun/c-Fos transactivation to the heterologous SV40 promoter. These functions are mediated by the AP-1 binding sites as multiple copies of the region A motif also confer TPA induction and c-Jun/c-Fos transactivation upon a heterologous promoter.
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PMID:Distal AP-1 binding sites mediate basal level enhancement and TPA induction of the mouse heme oxygenase-1 gene. 140 Apr 99

We have previously shown that the multidrug-resistance/P-glycoprotein gene, mdr3/mdr1a, is activated in mouse hepatocellular carcinomas (HCC). In this study, we show that in a number of HCC-derived cell lines (Hepa1c1c, Hepa1c1c-BprC1, and Hepa1-6) mdr3 is expressed at high levels. To investigate transcriptional regulation of mdr3 in these cells, we have isolated a DNA fragment containing the 5' portion of the mouse mdr3 gene and performed a functional analysis of its promoter. Transient transfection assays using various lengths of the promoter sequence to direct expression of the chloramphenicol acetyltransferase (CAT) reporter gene revealed that the sequence located -94 nucleotides upstream from mouse mdr3 transcription start site functions as a negative element in mouse hepatoma cells. A canonical AP-1 binding sequence TGA-GTCA located at -117 is at least in part responsible for the negative effect from the following observations: (i) Alteration of this AP-1 sequence by site-directed mutagenesis enhanced CAT expression. (ii) Expression of CAT reporter gene was elevated when double-stranded DNA containing the AP-1 sequence, but not mutated sequences, was used as a competitor in cotransfection experiment. (iii) Enhancement of the CAT expression was also seen in cotransfection experiments using recombinant plasmid DNA expressing the c-jun/c-fos proteins, which interact with AP-1 sequences. Interestingly, the proximal region of the hamster pgp1 promoter shares striking sequence similarity with that of the mouse mdr3 gene, including the AP-1 site, but the AP-1 site in the hamster promoter serves as a positive regulator. Although previous studies have demonstrated that positive and negative transcription factors can modulate gene expression through interactions with c-jun/c-fos, this is the first study to show that an AP-1 site functions as a negative cis-element in the regulation of gene expression.
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PMID:Structural and functional analyses of the promoter of the murine multidrug resistance gene mdr3/mdr1a reveal a negative element containing the AP-1 binding site. 168 3

cAMP and phorbol esters mediate cellular metabolism by the activation of distinct signal transduction pathways consisting of a cascade of sequential protein phosphorylations. An important consequence of the activation of these pathways is the stimulation of gene transcription by way of interactions of specific proteins with DNA control elements. The 8-base-pair (bp) DNA consensus sequence TGACGTCA [cAMP response element (cAMP-RE)] has been shown to confer cAMP responsivity on transcription from various promoters, and the closely related 7-bp consensus sequence TGA-(C or G)TCA [phorbol 12-myristate 13-acetate response element (PMA-RE)] lends transcriptional responsiveness to phorbol esters. In the JEG-3 placental cell line we find that several variants of the cAMP-REs fused to a gonadotropin alpha promoter chloramphenicol acetyltransferase reporter gene mediate responsiveness to cAMP but not to phorbol esters. The PMA-RE is responsive to phorbol esters but also imparts submaximal sensitivity to cAMP in the JEG-3 cells and in the Hep G2 hepatoma cell line. The transcriptional activities of cAMP-RE and PMA-RE are markedly influenced by the composition of the neighboring bases, but different sequences are permissive for the activity of the cAMP-RE versus the PMA-RE. The two signaling agents together display a supraadditive effect on reporter genes containing active PMA-REs but not cAMP-REs. Gel-mobility-shift and UV cross-linking analyses show that distinct proteins bind to the two control elements. One protein of 38 kDa binds to the cAMP-RE and several proteins of 48-84 kDa bind to the PMA-RE.
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PMID:Cyclic AMP and phorbol ester-stimulated transcription mediated by similar DNA elements that bind distinct proteins. 284 47