FIG. 5.

Effect of mutation of the CRS on cumulative CAT expression from the R₂ enhancer-containing US3 promoter at various times after infection. HFF cells were infected with approximately 5 PFU/cell, and the amount of CAT activity per microgram of protein was determined at various times after infection as described in Materials and Methods. (A) CAT activity at early times after infection; (B) CAT activity at early and late times after infection.