Molecular mechanism of basal CYP3A4 regulation by hepatocyte nuclear factor 4a: Evidence for direct regulation in the intestine

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dc.contributor.authorTegude, H.
dc.contributor.authorSchnabel, A.
dc.contributor.authorZanger, U.
dc.contributor.authorKlein, K.
dc.contributor.authorEichelbaum, M.
dc.contributor.authorBurk, O.
dc.date.issued2007
dc.description.abstractCytochrome P450 3A4 plays an outstanding role in the metabolism of clinically used drugs and shows a marked interindividual variability in expression even in the absence of inducing agents. Thus, regulation of basal expression contributes considerably to variability. The nuclear receptor hepatocyte nuclear factor 4 (HNF4) was previously shown to be associated with basal hepatic CYP3A4 expression. As how HNF4 regulates basal expression of CYP3A4 still remains elusive, we systematically screened 12.5 kilobase pairs (kb) of the CYP3A4 5' upstream region for activation by the receptor in the human intestinal cell line LS174T. In this study, we newly identified two widely separated regions mediating the activation by HNF4: a far distal region at -9.0 kb and the proximal promoter region at -0.2 kb. By gel shift experiments and transient transfections, we characterized direct repeat (DR) 1-type motifs in both regions as functional HNF4 response elements. Cooperation of the two regions was shown to be required for maximal activation by HNF4. The effect of HNF4 was antagonized by chicken ovalbumin upstream promoter transcription factor II, which was shown to bind to one of the DR1 motifs. Furthermore, activation of CYP3A4 via the DR1 element in the proximal promoter depends on an additional, yet unknown, factor, which is binding at -189 base pairs. Physiological relevance of this position for activation by HNF4 in vivo is suggested by the presence of a binding activity in small intestine similar to that in LS174T cells. In summary, we here have elucidated a molecular mechanism of direct regulation of CYP3A4 by HNF4, which is probably specific for the intestine.
dc.description.statementofresponsibilityHeike Tegude, Anke Schnabel, Ulrich M. Zanger, Kathrin Klein, Michel Eichelbaum, and Oliver Burk
dc.identifier.citationDrug Metabolism And Disposition, 2007; 35(6):946-954
dc.identifier.doi10.1124/dmd.106.013565
dc.identifier.issn0090-9556
dc.identifier.issn1521-009X
dc.identifier.urihttp://hdl.handle.net/2440/44121
dc.language.isoen
dc.publisherAmer Soc Pharmacology Experimental Therapeutics
dc.rightsCopyright © 2007 by the American Society for Pharmacology and Experimental Therapeutics.
dc.source.urihttps://doi.org/10.1124/dmd.106.013565
dc.subjectIntestinal Mucosa
dc.subjectLiver
dc.subjectCell Line, Tumor
dc.subjectHumans
dc.subjectCytochrome P-450 Enzyme System
dc.subjectRNA, Messenger
dc.subjectBinding Sites
dc.subjectResponse Elements
dc.subjectCytochrome P-450 CYP3A
dc.subjectHepatocyte Nuclear Factor 4
dc.subjectPromoter Regions, Genetic
dc.titleMolecular mechanism of basal CYP3A4 regulation by hepatocyte nuclear factor 4a: Evidence for direct regulation in the intestine
dc.typeJournal article
pubs.publication-statusPublished

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