Loss of CYP3A7 gene induction by 1,25-dihydroxyvitamin D3 is caused by less binding of VDR to the proximal ER6 in CYP3A7 gene.
Cytochrome P450 3A4 and 3A7 (CYP3A4 and CYP3A7, respectively) are predominant forms in the human adult and fetal liver, respectively. 1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is known to be a potent inducer of CYP3A4 in human colon carcinoma Caco-2 via vitamin D receptor (VDR). However, whether CYP3A7 is inducible by 1,25(OH)(2)D(3) has not yet been elucidated. In the present study, we examined the effect of 1,25(OH)(2)D(3) on CYP3A7 gene expression in Caco-2 cells, which express CYP3A4 and CYP3A7 mRNAs. 1,25(OH)(2)D(3) hardly induced the expression of CYP3A7 mRNA in contrast to the marked induction of CYP3A4 mRNA. Reporter assay using 5'-franking region CYP3A4 and CYP3A7 genes also revealed that 1,25(OH)(2)D(3) activates CYP3A4 promoter, but not CYP3A7 promoter, which has two mutations in the proximal ER6 site compared with CYP3A4 promoter. In addition, we found that the binding of VDR to the proximal ER6 in CYP3A7 gene was markedly less than that to the proximal ER6 in CYP3A4 gene using gel shift assay. Taken together, the decrease of VDR binding to the proximal ER6 caused by the mutation results in the loss of CYP3A7 gene activation by 1,25(OH)(2)D(3).
Hara
Hirokazu
H
Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, 5-6-1 Mitahora-higashi, Gifu 502-8585, Japan. harah@gifu-pu.ac.jp
Yasunami
Yoko
Y
Adachi
Tetsuo
T
D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D018938:Caco-2 Cells; D002117:Calcitriol / Q000494:pharmacology*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D004247:DNA / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D018167:Receptors, Calcitriol / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid; D015533:Transcriptional Activation; D014162:Transfection
D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C104464:CYP3A protein, human; C103123:CYP3A7 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D002117:Calcitriol