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 gene encoding aromatase P-450 (CYP XIX) has been isolated from two types of human genomic DNA libraries. It spans at least 70 kb and consists of 10 exons. The translational initiation site and the termination site are located in exon 2 and exon 10, respectively. The promoter region of the gene contains a TATA box, a CAAT box and two putative AP-1 binding sites beginning at -28, -83, -55 and -68 bp, respectively, from the transcriptional initiation site. In addition, a palindromic nucleotide sequence is observed between -209 and -196 and two types of repetitious hexanucleotide (consensus: AATGAA and CCATAAGG) are also present within the regions between -485 and -433 and between -358 and -331. Transient expression studies of chloramphenicol acetyltransferase constructs bearing various lengths of 5'-flanking region of the gene show that the region between -500 and -243 contains negative cis-acting element(s), whereas the region between -242 and -183 is required for efficient transcriptional activity. Northern blot analysis demonstrates that the expression of aromatose P-450 gene is remarkably stimulated by treatment of cells with 12-O-tetradecanoyl-phorbol 13-acetate. By chloramphenicol acetyltransferase assay the region up to nucleotide position -242 relative to the transcriptional initiation site is shown to participate in the transcriptional responsiveness to this phorbol ester.
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PMID:Structural and functional characterization of human aromatase P-450 gene. 217 39

The human aromatase cytochrome P450 gene, CYP 19, spans more than 75 kb in the human genome. Recently, it is proposed that the expression of the CYP 19 gene is regulated in part by tissue-specific promoters through the use of mechanisms involving alternative splicing of a number of untranslated exons. In this study, we have characterized cis-acting elements involved in the transcriptional regulation of the gene in human placental cells, where the majority of the transcripts contain the 5'-untranslated sequence encoded by exon I.1. By transient expression analyses in human BeWo choriocarcinoma cells using the bacterial chloramphenicol acetyltransferase gene as a reporter gene, we localized an enhancer element in the region between -242 and -166 relative to the major cap site of the gene. Furthermore, we demonstrate that the element between -2141 and -2115 participates in the 12-O-tetradecanoylphorbol 13-acetate (TPA)-mediated enhancement of gene expression. By screening a human placental cDNA expression library, we have isolated a cDNA clone (lambda 1-2) encoding a peptide which binds specifically to the element between -2141 and -2115. Sequence analysis of the clone revealed that the insert of lambda 1-2 encodes a part of the amino acid sequence of NF-IL6 (also termed as LAP and C/EBP beta). Northern blot analysis reveals expression of the NF-IL6 gene in BeWo cells and human placenta. These results indicate that NF-IL6 is one of the nuclear factors which participate in TPA-mediated transcriptional enhancement of CYP 19 gene expression.
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PMID:Transcriptional regulation of the human aromatase cytochrome P450 gene expression in human placental cells. 762 51

CYP3 A4 is the adult-specific form of cytochrome P450 in human livers [Komori, M., Nishio, K., Kitada, M., Shiramatsu, K., Muroya, K., Soma, M., Nagashima, K. & Kamataki, T. (1990) Biochemistry 29, 4430-4433]. The sequences of three genomic clones for CYP3A4 were analyzed for all exons, exon-intron junctions and the 5'-flanking region from the major transcription site to nucleotide position -1105, and compared with those of the CYP3A7 gene, a fetal-specific form of cytochrome P450 in humans. The results showed that the identity of 5'-flanking sequences between CYP3A4 and CYP3A7 genes was 91%, and that each 5'-flanking region had characteristic sequences termed as NFSE (P450NF-specific element) and HFLaSE (P450HFLa specific element), respectively. A basic transcription element (BTE) also lay in the 5'-flanking region of the CYP3A4 gene as seen in many CYP genes [Yanagida, A., Sogawa, K., Yasumoto, K. & Fujii-Kuriyama, Y. (1990) Mol. Cell. Biol. 10, 1470-1475]. The BTE binding factor (BTEB) was present in both adult and fetal human livers. To examine the transcriptional activity of the CYP3A4 gene, DNA fragments in the 5'-flanking region of the gene were inserted in front of the simian virus 40 promoter and the chloramphenicol acetyltransferase structural gene, and the constructs were transfected in HepG2 cells. The analysis of the chloramphenicol acetyltransferase activity indicated that (a) specific element(s) which could bind with a factor(s) in livers was present in the 5'-flanking region of the CYP3A4 gene to show the transcriptional activity.
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PMID:Gene structure of CYP3A4, an adult-specific form of cytochrome P450 in human livers, and its transcriptional control. 826 49

The CAT-Tox (L) assay has recently been developed and validated for detecting and quantifying the specific molecular mechanisms that underlie toxicity of various xenobotic chemicals. We performed this assay to measure the transcriptional responses associated with 2,4,6-trinitrotoluene (TNT) and 2 of its byproducts [2,4 and 2,6-dinitotoluenes (DNTs)] to 13 different recombinant cell lines generated from human liver carcinoma cells (HepG2) by creating stable transfectants of mammalian promoter chloramphenicol acetyltransferase (CAT) gene fusions. Cytoxicity test with the parental HepG2 cells, using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide]-based assay for cell viability, yielded LC50 values of 105 +/- 6 mg/mL for TNT in 1% dimethyl sulfoxide (DMSO), and > 300 mg/mL for DNTs, upon 48 h of exposure. TNT appeared to be more toxic than 2,4-DNT, which also showed a higher toxicity compared to 2,6-DNT. Of the 13 recombinant constructs evaluated, 8 (CYP 1A1, GST Ya, XRE, HMTIIA, c-fos, HSP70, GADD153, and GADD45), 5 (c-fos, HSP70, GADD153, GADD45, and GRP78), and none showed inductions to significant levels (p < 0.05), for TNT, 2,4-DNT, and 2,6-DNT, respectively. For most constructs, the induction of stress genes was concentration-dependent. These results show the potential for TNT and 2,4-DNT to cause protein damage and/or perturbations of protein biosynthesis (HSP70 and GRP78), alterations in DNA sequence or its helical structure (c-fos, GADD153, GADD45), and the potential involvement of TNT in the biotransformation process (CYP 1A1, GST Ya, XRE), and in the toxicokinetics of metal ions (HMTIIA). Within the range of concentrations tested (0-300 mg TNT or DNT/mL in 1% DMSO), no significant inductions (p > 0.05) of NFKBRE, p53RE, CRE, and RARE were found.
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PMID:Transcriptional activation of stress genes and cytotoxicity in human liver carcinoma cells (HepG2) exposed to 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, and 2,6-dinitrotoluene. 1140 92

Recent studies in our laboratory indicated that arsenic trioxide has the ability to cause significant cytotoxicity, and induction of a significant number of stress genes in human liver carcinoma cells, HepG2. However, similar investigations with atrazine did not show any significant effects of this chemical on HepG2 cells, even at its maximum solubility of 100 microg/mL in 1% dimethyl sulfoxide (DMSO). Further cytogenetic studies were therefore carried out to investigate the combined effects of arsenic trioxide and atrazine on cell viability and gene expression in immortalized human hepatocytes. Cytotoxicity was evaluated using the MTT-assay for cell viability, while the CAT-Tox (L) assay was performed to measure the induction of stress genes in thirteen different recombinant cell lines generated from human liver carcinoma cells (HepG2), by creating stable transfectants of different mammalian promoter-chloramphenicol acetyltransferase (CAT) gene fusions. Cytotoxicity experiments yielded LC50 values of 11.9 +/- 2.6 microg/mL for arsenic trioxide in de-ionized water, and 3.6 +/- 0.4 microg/mL for arsenic trioxide in 100 microg/mL atrazine; indicating a 3 fold increase in arsenic toxicity associated with the atrazine exposure. Co-exposure of HepG2 cells to atrazine also resulted in a significant increase in the potency of arsenic trioxide to upregulate a number of stress genes including those of the glutathione-S-transferase Ya subunit--GST Ya, metallothioneinIIa--HMTIIA, 70-kDa heat shock protein--HSP70, c-fos, 153-kDa growth arrest and DNA damage (GADD153), 45-kDa growth arrest and DNA damage (GADD45), and 78-kDa glucose regulated protein--GRP78 promoters, as well as the xenobiotic response element--XRE, tumor suppressor protein response element--p53RE, cyclic adenosine monophosphate response element--CRE, and retinoic acid response element--RARE. No significant changes were observed with respect to the influence of atrazine on the modulation of cytochrome P450 1A1-CYP 1A1, and nuclear factor kappa (B site) response element--NFkappaBRE by arsenic trioxide. These results indicate that co-exposure to atrazine strongly potentiates arsenic trioxide-induced cytotoxicity and transcriptional activation of stress genes in transformed human hepatocytes.
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PMID:Atrazine potentiation of arsenic trioxide-induced cytotoxicity and gene expression in human liver carcinoma cells (HepG2). 1167 11