FIG 5.

Mutational analysis of the 15-bp ORF52 promoter reveals a stringent sequence requirement for the TATT box. (A) Systematic single mutations. The 15-bp ORF52 promoter was mutated by individually changing each nucleotide of the 15 bp to the other three possible nucleotides. Fold activation was derived from comparing the promoter activity in the infected cells to that in the uninfected cells. The percentage of WT activation was calculated based on the fold activation for the WT reporter, set as 100%. The WT sequence of the 15-bp promoter is shown under the graph, and a gray box represents the region least tolerant to mutations. (B) Targeted double mutations. Three double mutations were tested, and the results are presented together with corresponding single mutations. The sequence of each 15-bp promoter is shown with WT nucleotides in lowercase and the specific mutations in underlined uppercase letters. Activation was calculated as described for panel A and is based on comparisons to fold activation for the WT 15-bp ORF52 promoter.