FIGURE 6.

Active AhR response element in human and mouse 5′-flanking region. Shown is activity of human (A) and mouse (B) 5′-flanking sequence in the Abcb6 gene in response to B[a]P. C, schematic representation of the 5′-flanking region of human and mouse Abcb6 genes. Core AhREs are shown as boxes with respective locations of the 5′ end base from the reported transcription start sites. D, schematic representation of the human ABCB6 promoter, used in the transactivation studies, showing the introduction of mutations in the AhRE. Gray shaded boxes show the AhR sequence motif that was mutated by site-directed mutagenesis on the human ABCB6 promoter. E, mutation of either the distal AhRE or all of the three AhREs does not activate the promoter-luciferase reporter in response to B[a]P. Values represent mean ± S.D. (error bars) (n = 3). Results representative of six independent experiments. *, significantly different from empty vector-transfected cells treated with B[a]P and ABCB6 promoter-transfected cells treated with vehicle. p < 0.01. #, significantly different from ABCB6-WT, ABCB6-M1, and ABCB6-M2 promoter-transfected cells treated with B[a]P. p < 0.01.