Figure 3.

Induction of apoptosis by E4orf4 mutant proteins. (A) The results from Fig. 2C are shown again, with the mutants arranged by descending intensity of their physical interaction with PP2A. (B) H1299 cells were cotransfected with the cell surface marker (Thy1.2) and the various E4orf4 mutant constructs. Apoptosis was measured by determining the levels of sub-G₁ cells appearing in the transfected cell population, stained with the fluorescent Thy1.2-specific antibodies. Background levels were determined either in the absence of E4orf4 (CMV) or in cells transfected with the antiapoptotic adenovirus E1B–19-kDa protein. Apoptosis induced by wt E4orf4 (in 25–35% of the cells, 48 hr posttransfection) was defined as 100%. The average of four experiments is shown.