reporter assay in Huh7 cells stably transfected with the GLI1 expressing plasmid. The four reporter plasmids each displayed different levels of promoter activity, but all displayed notably stronger promoter activity than the pGL3-basic control plasmid (Figure 5C). The pGL3−1307 plasmid displayed the strongest promoter activity. Remarkably, when the fragment between −1307 bp and −676 bp was deleted, the luciferase activity was almost abolished. The pGL3−1350 plasmid containing the −1350/−652 bp CtBP2 promoter fragment displayed the second highest promoter activity level of the transfected Huh7 CtBP2 cells. These data suggested the existence of a critical positive regulatory element in the −1350/−652 bp CtBP2 promoter fragment. To further investigate the importance of the −1350/−652 bp CtBP2 promoter fragment we examined pGL3−1350 luciferase activity in Huh7 cells transfected with a GLI1 expressing plasmid (Huh7 GLI1) or a control plasmid (Huh7 Vector). We observed that elevated GLI1 expression increased the luciferase activity of the pGL3−1350 reporter plasmid (Figure 5D).
