Por favor, use este identificador para citar o enlazar este Item:http://hdl.handle.net/20.500.12105/17520
Título
Transcriptional regulation of human CYP3A4 basal expression by CCAAT enhancer-binding protein alpha and hepatocyte nuclear factor-3 gamma.
Autor(es)
Fecha de publicación
2003-05
Cita
Mol Pharmacol . 2003;63(5):1180-9.
Idioma
Inglés
Tipo de documento
preprint
Resumen
Cytochrome P450 3A4 (CYP3A4) is involved in the metabolism of more than 50% of currently used therapeutic drugs, yet the mechanisms that control CYP3A4 basal expression in liver are poorly understood. Several putative binding sites for CCAAT/enhancer-binding protein (C/EBP) and hepatic nuclear factor 3 (HNF-3) were found by computer analysis in CYP3A4 promoter. The use of reporter gene assays, electrophoretic mobility shift assays, and site-directed mutagenesis revealed that one proximal and two distal C/EBP alpha binding sites are essential sites for the trans-activation of CYP3A4 promoter. No trans-activation was found in similar reporter gene experiments with a HNF-3 gamma expression vector. The relevance of these findings was further explored in the more complex DNA/chromatin structure within endogenous CYP3A4 gene. Using appropriate adenoviral expression vectors, we found that both hepatic and nonhepatic cells overexpressing C/EBP alpha had increased CYP3A4 mRNA levels, but no effect was observed when HNF-3 gamma was overexpressed. In contrast, overexpression of HNF-3 gamma simultaneously with C/EBP alpha resulted in a greater activation of the CYP3A4 gene. This cooperative effect was hepatic-specific and also occurred in CYP3A5 and CYP3A7 genes. To investigate the mechanism for HNF-3 gamma action, we studied its binding to CYP3A4 promoter and the effect of the deacetylase inhibitor trichostatin A. HNF-3 gamma was able to bind CYP3A4 promoter at a distal position, near the most distal C/EBP alpha binding site. Trichostatin A increased C/EBP alpha effect but abolished HNF-3 gamma cooperative action. These findings revealed that C/EBP alpha and HNF-3 gamma cooperatively regulate CYP3A4 expression in hepatic cells by a mechanism that probably involves chromatin remodeling.
MESH
Gene Expression Regulation, Enzymologic | Transcription Factors | Transcription, Genetic | Adenoviridae | CCAAT-Enhancer-Binding Protein-alpha | Cells, Cultured | Cytochrome P-450 CYP3A | Cytochrome P-450 Enzyme System | DNA-Binding Proteins | Enzyme Inhibitors | Genetic Vectors | Hepatocyte Nuclear Factor 3-gamma | Hepatocytes | Histone Deacetylase Inhibitors | Humans | Nuclear Proteins | Promoter Regions, Genetic | Transcriptional Activation | Transfection
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