Fig. (3) Effects of Single and Multiple NFI Mutations on Basal Activity of the HPV16 URR. The entire HPV16 URR (Fig. 1) was cloned into pGL3 (luciferase reporter vector, Promega) (pGL3/URR) where various NFI sites were mutated from GCCAA to GCAGA, which is unable to bind NFI. These constructs were transfected into HKc/HPV16, and luciferase activity was determined 68 to 72 h post transfection. Basal activity was calculated as the percent of wild type (up to 9.3 x 10⁵ RLU), and is shown for each mutant construct. Error bars indicate standard deviation (SD).