FIG. 6.

Effect of point mutations in the −19/+5 region on promoter activity. DI constructs with double promoters were used to measure the activity of each mutant promoter relative to the wild-type internal control (see Materials and Methods). The values obtained were then normalized against that obtained for the DIC20a construct, both of whose promoters were the wild-type −19/+5 promoter, and expressed as a percentage of wild-type activity. The top line shows the wild-type SIN sequence. Each value in subsequent lines corresponds to the promoter activity due to the base change at the indicated nucleotide position. For example, an A-to-G mutation at position −18 has 90% of wild-type activity.