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)

We have recently isolated cDNA clones representing four alternative splice forms of a T cell-specific transcription factor, TCF-1. Here we report the characterization of the human gene encoding this factor. The TCF-1 gene is contained in 10 exons including an untranslated first exon. The DNA-binding high mobility group (HMG) box of TCF-1 is encoded by the closely spaced exons VI and VII. Differential splicing involves an alternative exon (IX) and three splice acceptor sites in exon X. Based on comparison of sequence and on the placement of an alternative exon, TCF-1 appears closely related to the recently characterized HMG box transcription factor TCF-1 alpha/LEF. In particular, the HMG boxes encoded by the two TCF genes are virtually identical. The TCF-1 gene resides on chromosome 5 band q31.1. The TCF-1 promoter coincides with a CpG island. As determined by chloramphenicol acetyltransferase analysis, the promoter is preferentially active in T cells. The promoter does not contain TCF-1/TCF-1 alpha binding sites and is therefore not autoregulated. This observation implies the existence of yet uncharacterized T cell transcription factors that are active during early T cell differentiation.
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PMID:The human T cell transcription factor-1 gene. Structure, localization, and promoter characterization. 156 1

Receptor-bound growth factors elicit intracellular signals that lead to the phosphorylation and activation of numerous intracellular kinases and transcription factors with consequent changes in patterns of gene expression. Several oncogene products are able to mimic these signals, resulting in cell transformation and proliferation. For example, the introduction of oncogenic forms of Raf-1 kinase into fibroblasts induces transformation and leads to the constitutive expression of, among others, the c-fos proto-oncogene. Here it is shown that the elevation of c-fos promoter activity brought about by v-raf is mediated by TCF/Elk-1, which forms a ternary complex with SRF at the serum response element and is a substrate for mitogen-activating protein kinases in vitro. In NIH 3T3 fibroblasts, v-raf activates Erk2, and overexpression of an interfering mutant of Erk2 both blocks the ability of v-raf to activate the c-fos promoter and suppresses transformation. Mutation of individual mitogen-activating protein kinase phosphoacceptor sites in TCF/Elk-1 also compromises v-raf-activated expression of a Gal-Elk/Gal-chloramphenicol acetyltransferase reporter system. However, in at least one instance the introduction of glutamate, but not aspartate, at a phosphoacceptor site is compatible with activation. These results provide compelling evidence that phosphorylation of TCF/Elk-1 by Erk2 is a major link in the Raf-1 kinase-dependent signal transduction pathway that activates c-fos expression.
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PMID:Inhibition of v-raf-dependent c-fos expression and transformation by a kinase-defective mutant of the mitogen-activated protein kinase Erk2. 800 80

The functional role of the different sites binding transcriptional factors on the tissue-specific, glucose-responsive promoter of the L type pyruvate kinase gene (L-PK) has been investigated in transgenic mice. These sites are able to bind, from 3' to 5', HNF1, NF1, HNF4, and MLTF/USF, respectively. We have compared the level of chloramphenicol acetyltransferase reporter transgene expression when driven by a L-PK promoter fragment of either -96 base pairs (bp) (containing only the HNF1 binding site) or -150 bp (lacking the MLTF/USF binding site) or driven by a -183-bp L-PK promoter fragment with or without the NF1 binding site. Our results demonstrate that: 1) HNF1 alone is not sufficient to promote an efficient L-PK gene transcription in vivo; 2) with only binding sites for HNF1, NF1, and HNF4, though the tissue-specific pattern of expression is respected, the level of the gene transcription is low and the hormonal control is lost; 3) the MLTF/USF binding site is the target of the hormonal control, required for both positive response to carbohydrates and negative response to glucagon; 4) the role of NF1 in the promoter activity could be to negatively modulate the L-PK gene expression in the different tissues, without interfering with the glucose and hormone responsiveness.
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PMID:Exploration of a liver-specific, glucose/insulin-responsive promoter in transgenic mice. 831 45

LFB1 (HNF1) is a tissue-specific transcription factor found in the livers, stomachs, intestines, and kidneys of vertebrates. By analyzing the promoter of the Xenopus LFB1 gene, we identified potential autoregulation by LFB1 and regulation by HNF4, a transcription factor with a tissue distribution similar to that of LFB1. Injection of LFB1 promoter-chloramphenicol acetyltransferase constructs into Xenopus eggs revealed embryonic activation that is restricted to the region of the developing larvae expressing endogeneous LFB1. Proper embryonic activation was also observed with a rat LFB1 promoter. Deletion analysis of the Xenopus and rat promoters revealed that in both promoters embryonic activation is absolutely dependnet on the presence of an element that contains CCNCTCTC as the core consensus sequence. Since this element is recognized by the maternal factor OZ-1 previously described by N. Ovsenek, A. M. Zorn, and P. A. Krieg (Development 115:649-655, 1992), we might have identified the main constituents of a hierarchy that leads via LFB1 to the activation of tissue-specific genes during embryogenesis.
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PMID:Elements and factors involved in tissue-specific and embryonic expression of the liver transcription factor LFB1 in Xenopus laevis. 841 40

The L-II element (-149 to -126 bp) in the enhancer unit of the rat pyruvate kinase L (PKL) gene is required for cell-type-specific transcription and induction by carbohydrates. This element was found to bind multiple nuclear proteins with different heat stabilities. A heat-labile factor was shown to be hepatocyte nuclear factor (HNF) 4 by the electrophoretic mobility-shift assay (EMSA) using various competitor DNAs and anti-HNF4 serum. A heat-stable factor was purified from rat liver nuclear extract and was resolved as two protein bands migrating at about 33 kDa on SDS/polyacrylamide gels. Peptide sequence analysis revealed that these proteins were nuclear factor (NF) 1-L and NF1/Red1. The heat-stable factor was also identified as a member of the NF1 family by using various competitor DNAs and anti-NF1 serum in an EMSA. In addition, we found that a factor bound to the accessory site of the rat S14 gene, which is necessary for carbohydrate responsiveness of this gene, was also a member of the NF1 family, raising the possibility that the NF1 family is involved in the carbohydrate regulation of gene transcription by interactions with other proteins. The NF1 family members and HNF4 interacted with overlapping sequences of the L-II element, wherein the 5' half-site was more critical for NF1 binding, and the 3' site was more important for HNF4 binding. Co-transfection of a vector expressing either NF1-L or NF1/Red1 repressed the transcription of the PKL enhancer unit-chloramphenicol acetyltransferase (CAT) fusion gene in HepG2 cells, whereas co-transfection of a vector expressing HNF4 activated the transcription of the same reporter gene. Furthermore NF1 family members antagonized the effect of HNF4 on PKL enhancer unit-CAT fusion gene expression when both expression plasmids were co-transfected. We conclude that NF1 family members and HNF4 regulate transcription of the PKL gene in an opposing manner by binding overlapping sequences of the L-II element.
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PMID:Members of the nuclear factor 1 family and hepatocyte nuclear factor 4 bind to overlapping sequences of the L-II element on the rat pyruvate kinase L gene promoter and regulate its expression. 921 Apr 17

To identify the 5' sequences of the murine coagulation factor VII (fVII) gene that resulted in its efficient transcription, a variety of 5'-flanking sequences up to 7 kilobase pairs upstream of the translation ATG initiation codon were fused to the reporter gene, bacterial chloramphenicol acetyltransferase, and relative expression levels of this gene in mouse Hepa 1-6 cells were determined. It was found that the 5' region extending approximately 85 base pairs (bp) upstream of the transcriptional initiation site served as the minimal DNA region that provided full relative promoter activity for chloramphenicol acetyltransferase expression. This region of the gene also contains consensus sequences for liver-enriched transcription factors, C/EBP beta and HNF4, as well as for the ubiquitous protein factors, AP1, H4TF1, NF1, and Sp1. In vitro DNase I footprinting of the 200-bp proximal region of the promoter with a murine Hepa 1-6 cell nuclear extract revealed a clear footprint of a region corresponding to -80 to -28 bp of the murine fVII gene, suggesting that liver factors interact with this region of the DNA. Competitive gel shift and supershift assays with different synthetic oligonucleotide probes demonstrate that proteins contained in the nuclear extract, identified as C/EBP beta, H4TF1, and HNF4, bind to a region of the murine fVII DNA from 85 to 32 bp upstream of the transcription start site. Purified Sp1 also interacts with this region of the DNA at a site that substantially overlaps, but is not identical to, the H4TF1 binding locus. Binding of Sp1 to the mouse DNA was not observed with the nuclear extract as the source of the transcription factors, suggesting that Sp1 is likely displaced from its binding site by H4TF1 in the crude extract. In vivo dimethyl sulfate footprint analysis confirmed the existence of these sites and additionally revealed two other binding regions slightly upstream of the CCAAT/enhancer-binding protein (C/EBP) binding locus that are homologous to NF1 binding sequences. The data demonstrate that appropriate transcription factor binding sites exist in the proximal promoter region of the murine fVII gene that are consistent with its strong liver-based expression in a highly regulated manner.
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PMID:Characterization of transcriptional regulatory elements in the promoter region of the murine blood coagulation factor VII gene. 944 72

alpha-Fetoprotein (AFP), a protein highly induced during fetal liver development, is down-regulated by retinoids in the human hepatoma cell line Hep3B, in contrast to up-regulation observed in other cell types. Previously, we have documented that such up-regulation involves direct effects through cis-retinoid X receptor-binding sites in the AFP enhancer. In this report, we show a distinctive effect of all-trans-retinoic acid (RA) in Hep3B cells. RA caused a marked decrease in AFP transcripts. Deletion analysis of the upstream regulatory region of the AFP gene revealed that cis-acting sites required for down-regulation resided near the promoter. Gel mobility shift assays for factors binding to key elements in the AFP promoter region demonstrated that hepatocyte nuclear factor (HNF) 1 binding was diminished in nuclear extracts from RA-treated cells. In addition, HNF4, which is not known to bind to the AFP promoter but does regulate HNF1, was also diminished. The levels of HNF1 and HNF4 mRNA were also decreased following RA treatment. AFP promoter-chloramphenicol acetyltransferase transient transfection assays demonstrated that the level of HNF1 had a direct impact on basal transcription as well as RA-mediated down-regulation of the AFP gene, and that co-transfection of HNF1 and HNF4, but not transfection of either factor alone, reversed the RA-mediated inhibition. Taken together these data point to an interaction among the RA, HNF1, and HNF4 signals, which is reflected in decreased expression of AFP.
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PMID:Retinoic acid mediates down-regulation of the alpha-fetoprotein gene through decreased expression of hepatocyte nuclear factors. 979 24

We previously identified various upstream and downstream regulatory elements and factors important for hepatic expression of the human angiotensinogen (ANG) gene, the precursor of vasoactive octapeptide angiotensin II. In the present study, to further investigate the molecular mechanism of human ANG transcriptional regulation, we generated transgenic mice carrying the fusion gene composed of the 1. 3-kilobase promoter of the human ANG gene, its downstream enhancer, and the chloramphenicol acetyltransferase reporter gene. Because expression of the chloramphenicol acetyltransferase gene was observed strongly in the liver and weakly in the kidney, we suspected that hepatocyte nuclear factor (HNF) 4 with a tissue expression pattern similar to that of the reporter gene would regulate ANG transcription. In vitro assays indicated that HNF4 bound to the promoter elements and strongly activated the ANG transcription, but that chicken ovalbumin upstream promoter transcription factor (COUP-TF), a transcriptional repressor, dramatically repressed human ANG transcription through the promoter elements and the downstream enhancer core elements. Furthermore, COUP-TF dramatically decreased the human ANG transcription in the mouse liver by the Helios Gene Gun system in vivo. These results suggest that an interplay between HNF4 and COUP-TF could be important in hepatic human ANG transcription.
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PMID:Regulated expression of human angiotensinogen gene by hepatocyte nuclear factor 4 and chicken ovalbumin upstream promoter-transcription factor. 1057 24