AP-2-mediated regulation of human NAD(P)H: Quinone oxidoreductase 1 (NQO 1) gene expression

Abstract

NAD(P)H:quinone oxidoreductase 1 (NQO 1) is a flavoprotein that catalyzes two-electron reduction and detoxification of quinones. We have shown previously that twenty-four base pairs of the h uman A ntioxidant R esponse E lement (hARE) mediate basal and xenobiotic-induced expression of the NQO 1 gene [Li and Jaiswal, J Biol Chem 267: 15097–15104, 1992]. In the present report, we have characterized a second cis-element, AP-2, at nucleotide position −157 of the human NQO 1 gene promoter that regulates basal and cAMP-induced transcription of the NQO 1 gene. The NQO 1 gene AP-2-mediated expression of the chloramphenicol acetyl transferase (CAT) gene and the binding of nuclear proteins to the AP-2 element were observed in HeLa (AP-2 positive) cells but not in human hepatoblastoma Hep-G2 (AP-2 deficient) cells, indicating the involvement of transcription factor AP-2 in the regulation of NQO 1 gene expression. Affinity purification of nuclear protein that binds to the NQO 1 gene AP-2 DNA element and western analysis revealed that AP-2 indeed binds to the NQO 1 gene AP-2 element and regulates its expression in HeLa cells. The involvement of AP-2 in the regulation of NQO 1 gene expression was confirmed by the observation that cDNA-derived AP-2 protein in Hep-G2 cells increased in the NQO 1 gene AP-2 but not mutant AP-2 mediated expression of CAT gene in Hep-G2 cells.