Expression of Snk/Plk2 causes apoptosis in BL cells. BL lines DG75 (EBV^-) and Rael (EBV⁺) lacking endogenous Snk expression were transfected with Snk/Plk2 expression plasmids and analyzed by flow cytometry as described in “Materials and methods.” (A) Fluorescence-activated cell sorting (FACS) analysis shows sorting of successfully transfected cells based on GFP expression. (B) Western blot analysis shows expression of Snk/Plk2 protein in the GFP⁺ fraction but not in the negative fraction of sorted cells. (C) Cell-cycle analysis of GFP-sorted cells shows an increase in apoptosis in cells expressing Snk/Plk2. The figure shows (as indicated) non-transfected cells, cells receiving empty vector only, and 2 typical profiles of cells expressing Snk/Plk2. Essentially similar results were obtained with Rael (data not shown). (D) Histogram summarizes induction of apoptosis by expression of Snk/Plk2. The data shown are percent sub-G₁ (apoptotic) cells and are means ± 1 SD of 3 independent experiments.