title: Differences in transactivation between rat CYP3A1 and human CYP3A4 genes by human pregnane X receptor.
abstract: In an assay system using a human CYP3A4 reporter constructed with the promoter (+11 nt to -362 nt) and enhancer (-7.2 knt to -7.8 knt) regions including everted repeat separated by six nucleotides (ER-6) and direct repeat separated by three nucleotides (DR-3) motifs, the CYP3A4 transactivation was detected without overexpression of any nuclear receptors in rifampicin-treated HepG2 cells. Overexpression of human pregnane X receptor (hPXR) enhanced the transactivation. Rat CYP3A1 reporter constructed with the promoter region (+31 nt to -171 nt) including both DR-3 and ER-6 motifs was, however, not transactivated in rifampicin-treated cells, even after overexpression of hPXR. Although overexpression of retinoid X receptor alpha (RXRalpha) had no clear effect for both CYP3A reporters, co-expression of apolipoprotein AI regulatory protein-1 (ARP-1) with hPXR resulted in the rifampicin-induced transactivation of the CYP3A1 reporter. A truncated CYP3A4 reporter retaining the both motifs showed the rifampicin-induced transactivation by overexpression of hPXR and ARP-1, while the transactivation in hPXR-overexpressed cells was not observed. These results support the idea that a nuclear receptor other than RXRalpha may play a role in the CYP3A transactivation together with hPXR. The present study also suggests the involvement of a novel cis-element in the hPXR-mediated CYP3A4 transactivation.
authors.affiliation: Division of Drug Metabolism and Molecular Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University.
authors.forename: Tomonari
authors.initials: T
authors.lastname: Takada
authors.forename: Makoto
authors.initials: M
authors.lastname: Ogino
authors.forename: Masaaki
authors.initials: M
authors.lastname: Miyata
authors.forename: Miki
authors.initials: M
authors.lastname: Shimada
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Nagata
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yamazoe
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D024202:Electrophoretic Mobility Shift Assay; D004742:Enhancer Elements, Genetic / Q000235:genetics; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D000077297:Pregnane X Receptor; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics*; D011987:Receptors, Steroid / Q000235:genetics*; D013045:Species Specificity; D015533:Transcriptional Activation / Q000235:genetics*; D014162:Transfection
chemical_list: D000077297:Pregnane X Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C104464:CYP3A protein, human; C465138:Cyp3a23-3a1 protein, rat; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human