6.

Mutations in 7/8 abolish enhancer and ‘promoter’ activity. (A) Transient transfections of Caco2 cells using pGL3 reporter vector with inserted CFTR basal promoter and 7/8 in enhancer site. Middle bar represents construct with two bases mutated within HNF1 site (same bases changed with mutated EMSA probe). (B) 7/8 cloned as a ‘promoter’ (top bar) and with HNF1 site mutated (middle). Renilla luciferase vector used as transfection control in all experiments; normalized luciferase activity shown relative to pGL3 with CFTR basal promoter alone. Error bars represent standard error of the mean (n= 12), **P < 0.01 using unpaired t-tests comparing mutated and wild-type vectors.