FIG. 1.

Wild-type E4orf4 reduces colony formation by 293 cells. (A) 293 cells were transfected with 5 μg of pBabe-puro and 5 μg (total) of pCMV plus pCMV-E4orf4. The ratios between pCMV and pCMV-E4orf4 were varied, as indicated. Stable colonies were selected in 2.5 μg of puromycin per ml for 2 weeks. (B) 293 cells were transfected with 5 μg of the CMV vector, wild-type E4orf4 (wt), or mutant A3. Proteins were harvested 40 h posttransfection and subjected to Western blot analysis with an antibody specific to E4orf4. (C) 293 cells were transfected with 5 μg of pBabe-puro and 5 μg of effector plasmid (CMV, wild-type E4orf4, or mutant A3). Selection was carried out as described for panel A. The results are the mean of three experiments.