TAILIEUCHUNG - Báo cáo khoa học: Two CCAAT/enhancer binding protein sites in the cytochrome P4503A1 locus Potencial role in the glucocorticoid response

Induction of CYP3A genes by the ligand-activated preg-nane-X-receptor (PXR)involves the interaction of other as yet unidentified liver transcription factors. Here we show that the CYP3A1promoter contains two active sites con-trolled by the CCAAT/enhancer-binding protein a (C/ EBPa), previously shown to regulate a number of liver stress response genes. We have identified two functional C/EBP binding sites at theCYP3A1promoter that confer luciferase activity to C/EBPacotransfected CHO cells. | Eur. J. Biochem. 270 556-564 2003 FEBS 2003 doi Two CCAAT enhancer binding protein sites in the cytochrome P4503A1 locus Potencial role in the glucocorticoid response Elsa Rodrigues1 Marie-Jose Vilarem2 Vera Ribeiro1 Patrick Maurel2 and Maria C. Lechner1 1Molecular Biology Unit Faculty of Pharmacy University of Lisbon Portugal 2Unité 128 INSERM Montpellier France Induction of CYP3A genes by the ligand-activated preg-nane-X-receptor PXR involves the mteraction 4 other as yet unidentified liver transcription factors. Here we show that the CYP3A1 promoter contains two active sites controlled by the CCAAT enhancer-binding protein a C EBPa previously shown to regulate a number of liver stress response genes. We have identified two functional C EBP binding sites at the CYP3A1 promoter that confer luciferase activity to C EBPa cotransfected CHO cells. When inserted upstream of a thymidine kinase promoter oligonucleotides corresponding to these elements -350 -311 and -628 -608 increase reporter gene expression when cotransfected with a C EBPa expression vector. Point mutations in the most conserved nucleotides in either element prevent binding of C EBPa and abolish transactivation of the CYP3A1 promoter. Moreover we demonstrate that C EBPa accumulates in the rat liver nuclei in response to dexamethasone and that under these conditions C EBPa binds to the CYP3A1 promoter elements. Our results suggest a correlation between transcription of C EBPa nuclear protein function and induction of CYP3A1 by dexamethasone in the liver. They also support the notion that C EBPa participates in the up-regulation of the CYP3A1 gene in response to synthetic glucocorticoids. Keywords cytochrome P450 CYP3A1 locus C EBP regulatory elements glucocorticoid induction. Mammalian hepatic phenotypes are controlled through the concerted action of a number of liver-enriched transcription factors that act in cooperation with a number of ubiquitous and ligand-activated .

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