Fig. (4) NFI Binding Sites Exhibit Enhancer Function. A 69 bp enhancer element containing either 5 NFI consensus or mutant half sites was synthesized and cloned upstream of a CMV promoter / luciferase gene (pGL3 promoter, Promega). 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 70 h post transfection. The sequence for each enhancer element is shown, and the NFI consensus or mutant sites are underlined. Luciferase expression (RLU) is given for each construct. Error bars indicate standard deviation (SD).