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)

Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes; however, in certain human hepatoma cell lines, the growth is inhibited by HGF. In the present study, the effect of HGF on the alpha-fetoprotein (AFP) gene expression was analyzed in PLC/PRF/5 human hepatoma cells. HGF did not inhibit cell proliferation, but dose-dependently suppressed AFP secretion at the concentrations of 10 ng/ml or less. By Northern blot analysis, the levels of AFP mRNA were suppressed by HGF, whereas the levels of beta-actin mRNA used as a control did not show any significant changes. In the transient chloramphenicol acetyltransferase plasmid transfection assays, the AFP promoter activity was repressed by HGF, in contrast, the AFP enhancer activity was not affected by HGF. These results suggest that the AFP gene expression is down-regulated by HGF through the suppression of its promoter activity in human hepatoma cells.
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PMID:Hepatocyte growth factor down-regulates the alpha-fetoprotein gene expression in PLC/PRF/5 human hepatoma cells. 128 Apr 22

Epidermal growth factor (EGF) and 12-O-tetradecanoylphorbol-13-acetate (TPA) synergistically suppress activities of the promoter and enhancer of the human alpha-fetoprotein (AFP) gene in HuH-7 human hepatoma cells as analyzed by transient transfection assays using the chloramphenicol acetyltransferase gene as a reporter. In contrast to the AFP gene, albumin promoter and enhancer activities were not affected by EGF and TPA. Unexpectedly, however, Northern blot analysis revealed that the albumin mRNA level as well as the AFP mRNA level were reduced by treatment with EGF and TPA. We propose that in HuH-7 cells, the AFP enhancer stimulates the albumin promoter as well as the AFP promoter; and consequently, inhibition of the AFP enhancer by EGF and TPA results in reduction of both AFP and albumin mRNA levels. The significance of the involvement of the AFP enhancer in albumin transcription is discussed in relation to the inverse pattern of expression of the AFP and albumin genes in neonatal growth.
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PMID:A possible mechanism of inverse developmental regulation of alpha-fetoprotein and albumin genes. Studies with epidermal growth factor and phorbol ester. 137 Apr 67

We have compared the activities of mouse alpha-fetoprotein (AFP) enhancers I, II, and III with their minimal enhancer fragments (Mers) I, II, and III and with the entire 7-kilobase pair enhancer domain by transient expression assay in primary fetal mouse liver cells. The level of expression directed by the AFP promoter [p(-1009)AFPcat] alone is stimulated at least 10-fold by the entire AFP enhancer domain (-1009 to -6983). Enhancer I can drive the level of chloramphenicol acetyltransferase activity equivalent to that of the entire enhancer domain, whereas the increase in activity by enhancers II and III is significantly lower (1.5-fold). MersI, II, and III all mediate a greater increase in activity than their corresponding enhancer regions. The increase with MerI is 16-fold. Using DNase I protection analyses we identified 3 protein-binding regions in MerI; site Ia binds liver and brain nuclear proteins; site Ib binds liver, kidney, and brain nuclear proteins as well as purified C/EBP; site Ic binds liver and kidney nuclear proteins. Site-specific mutation of Ia, Ib, or Ic showed a 10-25% reduction in chloramphenicol acetyltransferase expression; deletion of the C/EBP-binding site in Ib showed a 45% reduction in activity and mutation of all 3 sites (Ia, Ib, and Ic) resulted in a 75% reduction in activity. Our studies indicate no single trans-acting factor is absolutely essential for enhancer activity, and that the enhancer activity of MerI is mediated via a combinatorial and additive mechanism.
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PMID:Functional analysis of the mouse alpha-fetoprotein enhancers and their subfragments in primary mouse hepatocyte cultures. 137 27

Cis-acting elements involved in the control of rat alpha-fetoprotein gene expression in the liver and its modulation by glucocorticoid hormones were detected after transfection of chloramphenicol acetyltransferase constructs and their transient expression into two hepatoma cell lines. The proximal promoter region (-324 to -15) was found to contain all the information necessary for tissue-specific expression. It is also involved in the negative gene modulation by glucocorticoids and includes an activating regulatory domain allowing efficient expression in the HepG2 cells. Three regions within 7 kilobase pairs of the 5' extragenic sequences are capable of stimulating the chloramphenicol acetyltransferase activity driven by the alpha-fetoprotein promoter sequence. One of these regions, at about -2.5 kilobase pairs, contains a short indivisible 170-base pair DNA element that fulfills all the criteria of a tissue-specific enhancer, i.e. orientation and position independence, as well as cell-specific stimulation of gene expression driven by a homologous or heterologous promoter. The enhancing properties of this element are totally abolished by glucocorticoids. DNase I footprinting experiments indicate that several rat liver nuclear proteins interact with this enhancer element.
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PMID:Regulation of the rat alpha-fetoprotein gene expression in liver. Both the promoter region and an enhancer element are liver-specific and negatively modulated by dexamethasone. 168 47

We studied the effects of transfection of the normal c-Ha-ras gene, rasGly-12, and its oncogenic mutant, rasVal-12, on expression of the alpha-fetoprotein (AFP) and albumin genes in a human hepatoma cell line, HuH-7. The mutant and, to a lesser extent, the normal ras gene caused reduction of the AFP mRNA but not the albumin mRNA level in transfected HuH-7 cells. Cotransfection experiments with a rasVal-12 expression plasmid and a chloramphenicol acetyltransferase reporter gene fused to AFP regulatory sequences showed that rasVal-12 suppressed the activity of enhancer and promoter regions containing A + T-rich sequences (AT motif). In contrast, rasVal-12 did not affect the promoter activity of the albumin and human hepatitis B virus pre-S1 genes even though these promoters contain homologous A + T-rich elements. ras transfection appeared to induce phosphorylation of nuclear proteins that interact with the AFP AT motif, since gel mobility analysis revealed the formation of slow-moving complexes which was reversed by phosphatase treatment. However, similar changes in complex formation were observed with the albumin and hepatitis B surface antigen pre-S1 promoters. Therefore, this effect alone cannot explain the specific down regulation of the AFP promoter and enhancer activity. ras-mediated suppression of the AFP gene may reflect the process of developmental gene regulation in which AFP gene transcription is controlled by a G-protein-linked signal transduction cascade triggered by external growth stimuli.
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PMID:c-Ha-ras down regulates the alpha-fetoprotein gene but not the albumin gene in human hepatoma cells. 169 Aug 41

We have identified cis-acting regulatory elements in the 5' flanking region of the mouse alpha-fetoprotein (Afp) gene, using the expression of the bacterial gene for chloramphenicol acetyltransferase (CAT) in a transient expression assay. Tissue-specific enhancer activity was determined by transfection of mouse hepatoma (BWTG3) and fibroblast cells (C127, NIH 3T3) with various DNA fragments linked to the CAT gene. A 5.4-kilobase restriction fragment was shown to have characteristics typical of enhancers, including the ability to function independent of orientation and position and the ability to enhance transcription from a heterologous promoter. The enhancer activity was greatest in the hepatoma cells, which express Afp. By deletion analysis, it was demonstrated that enhancer activity is present in several subfragments, indicating the presence of more than one element in this fragment. An additional regulatory element within 950 base pairs of the Afp transcription initiation site has been identified and shown to confer tissue-specific expression on the CAT gene. This fragment, which lacks enhancer activity, contains the Afp promoter region and mediates the tissue-specific expression of the CAT gene when driven by nonspecific viral enhancers. We conclude from our studies that there are several types of regulatory elements in the 5' flanking region of the Afp gene that help mediate tissue-specific expression.
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PMID:Liver-specific expression of the mouse alpha-fetoprotein gene is mediated by cis-acting DNA elements. 243 Feb 80

We describe experiments showing that the 5'-flanking region of the human alpha-fetoprotein (AFP) gene contains transcription control elements with characteristics of enhancers. The enhancer activity was detected and characterized by the ability to direct the expression of a linked chloramphenicol acetyltransferase (CAT) gene in transfected AFP-producing hepatoma cells in culture. The enhancer activity is cell-specific in that it occurs in hepatoma cells producing AFP, but not in non-AFP-producing hepatoma or nonhepatic cells. The active elements can direct CAT expression in conjunction with the SV40 promoter in an orientation- and position-independent manner. The sequences important for enhancer activity reside in the 400-base pair region between 3.3 and 3.7 kilobase pairs upstream of the AFP gene. This and proximal upstream regions contain multiple enhancer "core"-like sequences and other stretches of potential biological significance.
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PMID:Cell-specific enhancer activity in a far upstream region of the human alpha-fetoprotein gene. 243 18

The level of alpha-fetoprotein (AFP) mRNA in HuH-7 human hepatoma cells is elevated by the addition of dexamethasone to the culture medium. To locate the DNA region involved in hormonal regulation of the AFP gene, we constructed recombinant plasmids in which various lengths of the 5'-flanking sequence of the human AFP gene were fused to the CAT gene. Various cell lines were transfected with the recombinant plasmids, incubated with or without 3 x 10(-6) M dexamethasone, and then assayed for chloramphenicol acetyltransferase expression. In hepatoma cells that produce AFP, the dexamethasone treatment resulted in the stimulated chloramphenicol acetyltransferase expression when the transfected plasmids contained 169 base pairs (bp) or longer AFP 5'-flanking sequence. No dexamethasone effect was observed when the 5'-flanking sequence was less than 98 bp long. The dexamethasone stimulation was effectively suppressed by the glucocorticoid antagonist RU486, indicating that this effect is mediated by glucocorticoid receptors. The 71-bp region between positions -169 and -98 contains a nucleotide stretch which is similar to the consensus sequence of the glucocorticoid responsive element (GRE). Partial alterations of this sequence resulted in decreased dexamethasone response. The GRE-containing region stimulated heterologous (SV40) promoter activity in response to dexamethasone treatment in an orientation- and position-independent manner. The GRE and the upstream AFP enhancer function independently from each other.
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PMID:Transcriptional regulation of alpha-fetoprotein expression by dexamethasone in human hepatoma cells. 246 58

DNase I footprinting and gel mobility shift analysis showed that an HuH-7 hepatoma nuclear protein, termed AFP1, binds specifically to an AT-rich sequence, TGATTAATAATTACA, in domain B of the human alpha-fetoprotein enhancer. No such binding activity was found in HeLa cell nuclei. Transient transfection studies showed that a 54-base-pair region corresponding to the AFP1-binding site could stimulate the simian virus 40 early promoter to express a linked chloramphenicol acetyltransferase gene in an orientation-independent and cell-specific manner. The correlation between the binding of AFP1 and the stimulation of chloramphenicol acetyltransferase gene expression strongly suggests that specific interaction of AFP1 with the AT motif is important for cell-specific transcriptional enhancement. Competition gel mobility shift analysis revealed that similar AT-rich sequences with high affinities to AFP1 were also present in the promoters of the alpha-fetoprotein and albumin genes. These results suggest that AFP1 may function as a common regulatory factor in the transcription of the alpha-fetoprotein and albumin genes.
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PMID:Interaction of a hepatoma-specific nuclear factor with transcription-regulatory sequences of the human alpha-fetoprotein and albumin genes. 246 95

pAFP-CAT, a recombinant plasmid containing 5'-flanking sequence from -7 kb to +7 bp of rat alpha-fetoprotein (AFP) gene can drive the expression of the bacterial chloramphenicol acetyltransferase gene in McA-RH7777 and McA-RH8994 rat hepatoma cell lines. Dexamethasone treatment suppresses pAFP-CAT expression in McA-RH7777 cells but increases its expression in McA-RH8994 cells, which mimics the dexamethasone responses of the endogenous AFP gene in both cell lines. However, dexamethasone treatment enhanced pMMTV-CAT expression in both cell lines. These data suggest that the effects of dexamethasone on AFP gene expression may be mediated by different trans-acting factors binding to the specific cis-elements of the 5'-flanking region of the rat AFP gene.
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PMID:The mechanism of the bidirectional regulation of the rat alpha-fetoprotein gene by glucocorticoid hormone. 247 82


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