FIG. 4.

Autoregulation of CYP1A1 (BP-induced activity). HepG2 cells were transfected with the p1A1-FL plasmid (2 μg). In order to express the CYP1A1 protein, cells were cotransfected with 4 μg of the pRSV-1A1 expression vector (gray bars). In control cells (open bars), the same plasmid lacking the CYP1A1 cDNA (pRSV/MCS) was transfected in order to have an equivalent amount of total transfected DNA. All cells were cotransfected with pαglob-RL (1 μg) as an internal control. Results were expressed as the means ± standard errors of the means for the quotient of firefly luciferase activity and Renilla luciferase activity (n = 10), normalized to 100% for control cells transfected with pRSV/MCS. A statistical difference between pRSV/MCS and pRSV-1A1 for the same condition is marked with a double asterisk (P < 0.0001). All cells were treated by BP (2.5 μM) for 24 h before harvest. C, control cells; pLacI, cells cotransfected with the pLacI plasmid (1 μg); Catalase, cells treated with catalase (100 U/ml) for 24 h; and Ellipticine, cells treated with ellipticine (10 μM) for 24 h.