Enhancer activity in the first intron of the vecd gene. Four different fragments indicated by thick lines in this figure were prepared from the first intron of the VECD gene (a restriction map of the first intron was given at the top). Enhancer activity of each fragment was assessed by using the luciferase gene driven by 2.5-kbp 5′ promoter region of the VECD gene. Luciferase activity was measured either in NIH3T3 (□) or F2 (▪) after transient transfection of each construct. Each bar is the mean ± SD of 5 independent experiments.