title: CYP2A7 pseudogene transcript affects CYP2A6 expression in human liver by acting as a decoy for miR-126.
abstract: Human cytochrome P450 (CYP)2A6 is responsible for the metabolic activation of tobacco-related nitrosamines, as well as the metabolism of nicotine and some pharmaceutical drugs. There are large interindividual differences in CYP2A6 activity and expression, largely attributed to genetic polymorphisms. However, the variability was observed within homozygotes of the wild-type CYP2A6 gene. In this study, we investigated the possibility that CYP2A6 might be regulated by microRNA. A luciferase assay revealed that a microRNA recognition element (MRE) of miR-126* found in the 3'-untranslated region (UTR) of CYP2A6 mRNA is functional. We established two HEK293 cell lines stably expressing CYP2A6, with one including and the other excluding the full-length 3'-UTR (HEK/2A6+UTR and HEK/2A6 cells, respectively). Overexpression of miR-126* markedly decreased CYP2A6 protein levels, enzyme activity, and mRNA level in HEK/2A6+UTR cells, whereas it marginally decreased those in HEK/2A6 cells, indicating that the 3'-UTR including the MRE is functional for the downregulation of CYP2A6 by miR-126*. The inhibition of miR-126* increased CYP2A6 protein levels in primary human hepatocytes, suggesting that miR-126* downregulates endogenous CYP2A6 expression. In 20 human liver samples, the expression ratios of CYP2A6 and a pseudogene transcript CYP2A7 mRNA were highly variable (CYP2A7/CYP2A6: 0.1 to 12). Interestingly, we found that CYP2A7 was another target of miR-126* and restored the miR-126*-dependent downregulation of CYP2A6 by acting as a decoy for miR-126*. In conclusion, this study demonstrates that human CYP2A6 is post-transcriptionally regulated by miR-126* and that CYP2A7 affects CYP2A6 expression by competing for miR-126* binding.
authors.affiliation: Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Japan (M.Na., Y.F., S.-i.Y., T.F., T.Y., M.Ni.); Department of Legal Medicine, Iwate Medical University School of Medicine, Uchimaru, Morioka, Japan (M.T., Y.A.); and Department of Forensic Medicine, Nagoya City University Graduate School of Medical Sciences, Kawasumi, Nagoya, Japan (Y.A.).
authors.forename: Masataka
authors.initials: M
authors.lastname: Nakano
authors.affiliation: Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Japan (M.Na., Y.F., S.-i.Y., T.F., T.Y., M.Ni.); Department of Legal Medicine, Iwate Medical University School of Medicine, Uchimaru, Morioka, Japan (M.T., Y.A.); and Department of Forensic Medicine, Nagoya City University Graduate School of Medical Sciences, Kawasumi, Nagoya, Japan (Y.A.).
authors.forename: Yasunari
authors.initials: Y
authors.lastname: Fukushima
authors.affiliation: Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Japan (M.Na., Y.F., S.-i.Y., T.F., T.Y., M.Ni.); Department of Legal Medicine, Iwate Medical University School of Medicine, Uchimaru, Morioka, Japan (M.T., Y.A.); and Department of Forensic Medicine, Nagoya City University Graduate School of Medical Sciences, Kawasumi, Nagoya, Japan (Y.A.).
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Yokota
authors.affiliation: Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Japan (M.Na., Y.F., S.-i.Y., T.F., T.Y., M.Ni.); Department of Legal Medicine, Iwate Medical University School of Medicine, Uchimaru, Morioka, Japan (M.T., Y.A.); and Department of Forensic Medicine, Nagoya City University Graduate School of Medical Sciences, Kawasumi, Nagoya, Japan (Y.A.).
authors.forename: Tatsuki
authors.initials: T
authors.lastname: Fukami
authors.affiliation: Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Japan (M.Na., Y.F., S.-i.Y., T.F., T.Y., M.Ni.); Department of Legal Medicine, Iwate Medical University School of Medicine, Uchimaru, Morioka, Japan (M.T., Y.A.); and Department of Forensic Medicine, Nagoya City University Graduate School of Medical Sciences, Kawasumi, Nagoya, Japan (Y.A.).
authors.forename: Masataka
authors.initials: M
authors.lastname: Takamiya
authors.affiliation: Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Japan (M.Na., Y.F., S.-i.Y., T.F., T.Y., M.Ni.); Department of Legal Medicine, Iwate Medical University School of Medicine, Uchimaru, Morioka, Japan (M.T., Y.A.); and Department of Forensic Medicine, Nagoya City University Graduate School of Medical Sciences, Kawasumi, Nagoya, Japan (Y.A.).
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Aoki
authors.affiliation: Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Japan (M.Na., Y.F., S.-i.Y., T.F., T.Y., M.Ni.); Department of Legal Medicine, Iwate Medical University School of Medicine, Uchimaru, Morioka, Japan (M.T., Y.A.); and Department of Forensic Medicine, Nagoya City University Graduate School of Medical Sciences, Kawasumi, Nagoya, Japan (Y.A.).
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Yokoi
authors.affiliation: Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Japan (M.Na., Y.F., S.-i.Y., T.F., T.Y., M.Ni.); Department of Legal Medicine, Iwate Medical University School of Medicine, Uchimaru, Morioka, Japan (M.T., Y.A.); and Department of Forensic Medicine, Nagoya City University Graduate School of Medical Sciences, Kawasumi, Nagoya, Japan (Y.A.) nmiki@p.kanazawa-u.ac.jp.
authors.forename: Miki
authors.initials: M
authors.lastname: Nakajima
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D002460:Cell Line; D065637:Cytochrome P-450 CYP2A6 / Q000235:genetics*; D000072467:Cytochrome P450 Family 2; D015536:Down-Regulation / Q000235:genetics; D057809:HEK293 Cells; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000378:metabolism*; D035683:MicroRNAs / Q000235:genetics*; D011110:Polymorphism, Genetic / Q000235:genetics; D011544:Pseudogenes / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D020413:3' Untranslated Regions; C527111:MIRN126 microRNA, human; D035683:MicroRNAs; D012333:RNA, Messenger; D001189:Aryl Hydrocarbon Hydroxylases; C585710:CYP2A6 protein, human; C423964:CYP2A7 protein, human; D065637:Cytochrome P-450 CYP2A6; D000072467:Cytochrome P450 Family 2