Human NRH:
quinone oxidoreductase 2 (
NQO2) is a cytosolic
protein that catalyzes the metabolic reduction of
quinones and provides protection against myelogenous
hyperplasia and chemical
carcinogenesis.
NQO2 gene expression is induced in response to
antioxidant tert-butylhydroquinone (
tBHQ). Sequence analysis revealed six putative antioxidant response elements (ARE1 through 6) in the human
NQO2 gene promoter. Deletion mutagenesis and transfection studies suggested that the ARE region between
nucleotides -1433 and -1424 is essential for basal expression and
antioxidant induction of
NQO2 gene expression. Mutation of this ARE from 3.8 kb
NQO2 gene promoter significantly repressed expression and abrogated the induction in response to
antioxidant in transfected cells. Band shift, supershift, and
chromatin immunoprecipitation (ChIP) assays demonstrated binding of nuclear factors Nrf2 and JunD with human
NQO2 gene ARE. Coimmunoprecipitation experiments revealed an association between Nrf2 and JunD. Overexpression of Nrf2 upregulated and overexpression of Nrf2 dominant-negative mutant downregulated ARE-mediated
NQO2 gene expression. The treatment of Hep-G2 cells with Nrf2-specific RNAi significantly reduced Nrf2 and
NQO2 gene expression and
tBHQ induction. The results combined demonstrated that Nrf2 associates with JunD, binds to ARE at
nucleotide -1433, and regulates human
NQO2 gene expression and induction in response to
antioxidants.