FIG. 6.
The S151D,S153D mutant is more active than wild-type Rex. 293 T cells (2 × 105) were transfected with 1 μg of pctat, 3 μg of pCgagRxRE-II, 1 μg of luciferase, and increasing concentrations (0.1 to 5 μg) of wild-type (WT) or rex mutant (M17 [S151A,S153A] or S151D,S153D) expression vectors. At 48 h posttransfection, cells were harvested and assayed for p24gag as described in Materials and Methods. Lysates were assayed for luciferase activity to control for transfection efficiency. The values represent actual p24gag levels for three independent experiments. Error bars indicate standard deviations. The results indicate that at lower DNA concentrations, Rex mutant S151D,S153D (exclusively in the p26rex conformation) is significantly more active than WT Rex.