(A) Identification of CPRE by functional assays in NIH3T3 cells. The effects of nucleotide transversions in the region between −51 and −40 were examined. The results are expressed as the ratios of luciferase activities to that obtained with a pGL3-Basic plasmid. Data are the means of triplicate determinations. (B) Various constructs with the indicated mutations were transfected into NIH3T3 cells. Results are the means of three separate experiments.