FIG. 3.

Autoregulation of CYP1A1 (basal activity). HepG2 cells were transfected with the p1A1-FL reporter plasmid (2 μg). (A) Structure of the 1.6-kb-long human CYP1A1 promoter used in transfection experiments (p1A1-FL vector). (B) Effect of the expression of CYP1A1 on the basal activity of the CYP1A1 promoter. 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 the 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).