FIGURE 3.

The RXL motif of Rb is dispensable for Rb phosphorylation by UL97. A, Saos-2 cells were transfected with expression plasmids for HA-tagged alleles of wild-type Rb or Rb in which the C-terminal 99 amino acids containing the RXL motifs were deleted (RxL) together with either an empty vector (EV) or one expressing V5-tagged WT UL97. Lysates harvested 48 h after transfection were analyzed by Western blotting with the indicated antibodies. B, Saos-2 cells were transfected with a luciferase reporter driven by the E2F1 promoter together with an expression plasmid for UL97 and either wild-type or RXL mutant Rb. Lysates harvested 48 h after transfection were analyzed for luciferase activity (top) and protein expression with the indicated antibodies (bottom). Luciferase activity was normalized to total protein concentration and is presented relative to the activity of the reporter without Rb or UL97 (set at 100%). Error bars denote the S.D. **, p < 0.01.