A conserved antioxidant response element ( ARE) in the promoter of human carbonyl reductase 3 ( CBR3) mediates induction by the master redox switch Nrf2

Abstract

Carbonyl reductase activity catalyzes the two electron reduction of several endogenous and exogenous carbonyl substrates. Recent data indicate that the expression of human carbonyl reductase 3 ( CBR3) is regulated by the master redox switch Nrf2. Nrf2 binds to conserved antioxidant response elements ( AREs) in the promoters of target genes. The presence of functional AREs in the CBR3 promoter has not yet been reported. In this study, experiments with reporter constructs showed that the prototypical Nrf2 activator tert-butyl hydroquinone (t-BHQ) induces CBR3 promoter activity in cultures of HepG2 (2.7-fold; p < 0.05) and MCF-7 cells (22-fold; p < 0.01). Computational searches identified a conserved ARE in the distal CBR3 promoter region ( −2698 ARE). Deletion of this ARE from a 4212-bp CBR3 promoter construct impacted basal promoter activity and induction of promoter activity in response to treatment with t-BHQ. Deletion of −2698 ARE also impacted the induction of CBR3 promoter activity in cells overexpressing Nrf2. Electrophoretic mobility shift assays (EMSA) demonstrated increased binding of specific protein complexes to −2698 ARE in nuclear extracts from t-BHQ treated cells. The presence of Nrf2 in the specific nuclear protein– −2698 ARE complexes was evidenced in EMSA experiments with anti-Nrf2 antibodies. These data suggest that the distal −2698 ARE mediates the induction of human CBR3 in response to prototypical activators of Nrf2.