Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

ATBF1 is a 306-kDa protein containing four homeodomains, 17 zinc finger motifs, and several segments potentially involved in transcriptional regulation (T. Morinaga, H. Yasuda, T. Hashimoto, K. Higashio, and T. Tamaoki, Mol. Cell. Biol. 11:6041-6049, 1991). At least one of the homeodomains of ATBF1 binds to an AT-rich element in the human alpha-fetoprotein (AFP) enhancer (enhancer AT motif). In the present work, we analyzed the transcriptional regulatory activity of ATBF1 with respect to the enhancer AT motif and similar AT-rich elements in the human AFP promoter and the human albumin promoter and enhancer. Gel retardation assays showed that ATBF1 binds to the AFP enhancer AT motif efficiently; however, it binds weakly or not at all to other AT-rich elements in the AFP and albumin regulatory regions studied. Alterations of the enhancer AT motif by site-specific mutagenesis resulted in the loss of binding of ATBF1. Cotransfection experiments with an ATBF1 expression plasmid and the chloramphenicol acetyltransferase (CAT) gene fused to AFP promoter or enhancer fragments showed that ATBF1 suppressed the activity of AFP enhancer and promoter regions containing AT-rich elements. This suppression was reduced when the mutated AT motifs with low affinity to ATBF1 were linked to the CAT gene. The ATBF1 suppression of AFP promoter and enhancer activities appeared to be due, at least in part, to competition between ATBF1 and HNF1 for the same binding site. In contrast to the AFP promoter and enhancer, the albumin promoter and enhancer were not affected by ATBF1, although they contain homologous AT-rich elements. These results show that ATBF1 is able to distinguish AFP and albumin AT-rich elements, leading to selective suppression of the AFP promoter and enhancer activities.
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PMID:ATBF1, a multiple-homeodomain zinc finger protein, selectively down-regulates AT-rich elements of the human alpha-fetoprotein gene. 750 6

The 5'-upstream region of the rat alpha-fetoprotein (AFP) gene strongly increased de novo methylation of an adjacent chloramphenicol acetyltransferase (CAT) gene upon transfection into F9 mouse embryonal carcinoma cells. The same effect was exerted by a distal 775-base pair (bp) fragment and by 300- and 1-kb fragments preceding the transcriptional start site, but not by other parts of the control region. Further division of the larger, strongly active fragments resulted in a gradual decrease of methylation and clonal variation in the methylation patterns. The effect of the 775-bp fragment did not depend on its orientation. It was ablated by insertion of the mouse metallothionein I promoter between the AFP gene fragment and the CAT gene, but not by its insertion upstream of the AFP gene fragment. Two fragments from the AFP control region increasing methylation contained B1 and B2 small interspersed repetitive elements, respectively. B1 and B2 sequences of different origin also acted strongly to increase methylation. These findings support the idea that mammalian genes contain specific sequences involved in regulating their methylation. The effects of these sequences appear to be exerted in cis, to be dependent on proximity, but not on orientation, and to require an optimal size of 500-700 bp. Small retrotransposon sequences within such elements may be particularly effective in attracting de novo methylation.
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PMID:Enhancement of reporter gene de novo methylation by DNA fragments from the alpha-fetoprotein control region. 750 85

Retinoic acid (RA) is widely involved in the control of cell proliferation and differentiation, as well as embryo pattern formation. Transcription of the oncodevelopmental protein, alpha-fetoprotein (AFP), is stimulated by retinoic acid (RA) in neoplastic cells. To study RA regulation of AFP gene expression, the 5'-flanking region of AFP gene was cloned and analyzed. In the present study, transfection of deletion mutants and sequence analysis revealed a retinoid X receptor response element (AFP-RXRE) located at position -139 to -127 of the AFP promoter. Synthetic AFP-RXRE was ligated into a reporter construct with the heterologous promoter and chloramphenicol acetyltransferase (CAT). AFP-RXRE conferred a marked RA responsiveness in the cotransfection with retinoid X receptor (RXR), but not with retinoic acid receptors (RARs). Consistent with these data, only RXR bound to AFP-RXRE with high affinity in the mobility shift assays. Chicken ovalbumin upstream promoter transcription factor (COUP-TF), an orphan member of the steroid/thyroid hormone superfamily, also demonstrated specific binding activity to AFP-RXRE in vitro. In cotransfection assays, COUP-TF dramatically repressed the transactivation of RXR on AFP-RXRE. The mechanism of repression by COUP-TF may involve the mutual occupancy of the AFP-RXRE binding site between RXR and COUP-TF.
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PMID:Transactivation and repression of the alpha-fetoprotein gene promoter by retinoid X receptor and chicken ovalbumin upstream promoter transcription factor. 751 61

High level expression of the alpha-fetoprotein (AFP) gene is controlled by three upstream enhancers which function even in hepatic cell lines that repress the AFP gene promoter. The most distal ("Complex 3," at -6 kilobases) is the strongest in HepG2 cells. We mapped the main activity of Complex 3 to a 170-base pair (BP) region from -6069 to -5900; progressive deletion of the 5'- and 3'-ends identified an 84-bp segment which accounted for 90% of enhancer activity. Expression studies, which combined the deleted Complex 3 with an AFP or tk promoter chloramphenicol acetyltransferase gene fusion, resolved five regions in the enhancer (Ia, Ib, II, III, and IV). Deletion of Regions Ia or II strongly reduced stimulation of the AFP promoter, while Regions Ia and Ib were essential for stimulation of the tk promoter. Footprinting indicated multiple binding sites in regions Ia, Ib, and II. Gel shift and oligonucleotide competition demonstrated that Regions Ia and II had high affinity HNF3- and C/EBP-binding sites, respectively, while additional unidentified factors bound throughout Regions I-III. Complex 3 is a powerful liver-specific transcriptional regulator and an important model of long distance gene activation.
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PMID:Characterization of the distal alpha-fetoprotein enhancer, a strong, long distance, liver-specific activator. 752 Sep 13

In McA-RH 8994 rat hepatoma cells, all-trans-retinoic acid (t-RA) induces expression of the alpha-fetoprotein (AFP) and albumin genes and results in a phenotype similar to differentiated fetal hepatocytes. The present study elucidated the mechanism involved in AFP gene regulation mediated by retinoic acid. Northern blot analyses demonstrated that 9-cis-retinoic acid (c-RA), a ligand for retinoid x receptors (RXRs), also induced expression of the AFP gene in McA-RH 8994 cells. The induction was time- and dose-dependent. Northern blots and transfection assays using the 7.3 kb full-length regulatory region of the AFP gene demonstrated that c-RA was more effective than t-RA in regulating expression of the AFP gene. At 10(-7) M, c-RA increased AFP mRNA 5-fold and chloramphenicol acetyltransferase (CAT) activity 2.5-fold. In contrast, t-RA at a concentration of 10(-7) M exerted no significant effect; 10(-6) to 10(-5) M t-RA was needed to affect AFP gene expression. These data suggested that activation of RXRs is essential for the regulation of the AFP gene. Co-transfection experiments revealed that over-expression of RXR alpha in McA-RH 8994 cells further enhanced the CAT activity induced by c-RA. In addition, c-RA did not alter the half-life of AFP mRNA. Thus, RXR alpha may play a crucial role in transcriptional regulation of the AFP gene and in controlling hepatocyte phenotype.
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PMID:9-cis-retinoic acid is more effective than all-trans-retinoic acid in upregulating expression of the alpha-fetoprotein gene. 753 13

To study the transcriptional regulation of the liver gluconeogenic phenotype, the underdifferentiated mouse Hepa-1c1c7 (Hepa) hepatoma cell line was used. These cells mimicked the fetal liver by appreciably expressing the alpha-fetoprotein and albumin genes but not the phosphoenolpyruvate carboxykinase (PEPCK) gene. Unlike the fetal liver, however, Hepa cells failed to express the early-expressed factors hepatocyte nuclear factor 1 alpha (HNF-1 alpha) and HNF-4 and the late-expressed factor C/EBP alpha, thereby providing a suitable system for examining possible cooperation between these factors in the transcriptional regulation of the PEPCK gene. Transient transfection assays of a chimeric PEPCK-chloramphenicol acetyltransferase construct showed a residual PEPCK promoter activity in the Hepa cell line, which was slightly stimulated by cotransfection with a single transcription factor from either the C/EBP family or HNF-1 alpha but not at all affected by cotransfection of HNF-4. In contrast, cotransfection of the PEPCK construct with members from the C/EBP family plus HNF-1 alpha resulted in a synergistic stimulation of the PEPCK promoter activity. This synergistic effect depended on the presence in the PEPCK promoter region of the HNF-1 recognition sequence and on the presence of two C/EBP recognition sequences. The results demonstrate a requirement for coexistence and cooperation between early and late liver-enriched transcription factors in the transcriptional regulation of the PEPCK gene. In addition, the results suggest redundancy between members of the C/EBP family of transcription factors in the regulation of PEPCK gene expression.
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PMID:Transcriptional regulation of the phosphoenolpyruvate carboxykinase gene by cooperation between hepatic nuclear factors. 793 27

Butyrolactone I is a selective inhibitor of the cyclin-dependent kinase (cdk) family, cdk2 and cdc2 kinase. In the present study, the effect of butyrolactone I on expression of the albumin and alpha-fetoprotein (AFP) genes was investigated in HuH-7 human hepatoma cells. Butyrolactone I inhibited cell growth and arrested cells predominantly in G2/M phase. By Northern blot analysis, the levels of both albumin and AFP mRNA were suppressed dose-dependently by butyrolactone I. In transient chloramphenicol acetyltransferase plasmid transfection experiments, the albumin promoter activity and the AFP promoter and enhancer activities were suppressed by butyrolactone I. Consistent with this, the transcripts of hepatocyte nuclear factor-1 (HNF-1), a liver-specific transcription factor which transactivates these promoter and enhancer regions were reduced by butyrolactone I in a dose-dependent manner. These results indicate that butyrolactone I down-regulates both the albumin and the AFP gene transcription through the reduction of HNF-1 expression.
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PMID:Suppression of albumin and alpha-fetoprotein gene expression by butyrolactone I, a selective inhibitor of the cdk family, in HuH-7 human hepatoma cells. 989 85


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