luciferase reporter plasmids containing one, two, three, and five tandem repeats of PPRE, and found that the induced luciferase activity is directly proportional to the number of PPREs present in the promoter region [28]. However, the maximal induction of luciferase activity was observed in HepG2 cells transfected with five or six tandem repeats of PPRE construct in this study. Therefore, we selected the construct containing five tandem repeats of PPRE for further experiment, and these findings suggested that induced luciferase activity might not be proportional to the number of PPREs.
