Functional analysis of <i>ATP8B1</i> promoter regions.

<p>HepG2 cells were transiently transfected with luciferase reporter gene constructs containing 12 different fragments of putative <i>ATP8B1</i> promoters. Nine luciferase constructs (Prom 1 to Prom 9) were designed to comprise the putative dominant promoter P3, two constructs covered promoter P1 (Proms 11 and 12) and one covered promoter P2 (Prom 10). The position of the tested fragments are indicated by horizontal double arrow lines. The number in brackets next to the construct name represents its size (bp). Prom 3 and Prom 4 were designed to include/exclude a putative FXR/RXR binding site indicated by black oval. Antisense construct encodes the same region as Prom 5, but in antisense orientation. Putative promoters (P1–P3) are depicted as horizontal thick arrows. Transcriptional activity for each construct was measured in relative light units per second (RLU/s) and corrected for the transfection efficiency using the internal control <i>Renilla</i> pRL-TK expression plasmid. The data shown are calculated from 3–5 independent experiments and related to the pGL3 Basic activity.