EBV's antiapoptotic function in both PTLD1 and Oku-BL cells is efficiently complemented by Bcl-XL and involves the repression of the proapoptotic protein Bim. (A) Cells were assayed for global cell death by staining cells with trypan blue. Dashed lines represent cells in which dnEBNA1 is induced; solid lines, cells in which dnEBNA1 remains uninduced. (Left graph) PTLD1 cells (clone P5-1 only shown) transduced with a control vector (gray lines) or a Bcl-XL expression vector (orange lines). (Right graph) Oku-BL cells (clone O2-4 only shown). For each time point, at least 200 cells were analyzed. The average of at least 3 independent experiments ± SD is reported. (B) The levels of endogenous Bim isoforms were analyzed by Western blotting in Oku-BL cells 14 days after induction of dnEBNA1 or in PTLD1 cells 12 days after induction. One of 2 independent experiments is shown. The levels of Bim were normalized to α-tubulin levels and then compared with control cells (dnEBNA1 off) whose normalized level was arbitrarily set to one. Bim isoforms L and S are not resolved on these blots.