FIG. 6.
The apoptosis of PKR-sufficient HeLa cells induced by ΔE3L vaccinia virus can be inhibited by caspase inhibitor. PKR+, PKRkd, and PKRkd-con HeLa cells were infected with ΔE3L mutant virus in the presence (+) or absence (−) of the caspase inhibitors z-VAD-fmk (100 μM) and DMSO (1%) or left uninfected. (A) Cytopathic effect as revealed by microscopy. Images were taken at 24 h p.i. (B) Western blot analysis. Whole-cell extracts were prepared 24 h p.i., and 10 μg protein was loaded in each lane. The membranes were probed with antibodies against PARP and with β-actin as a loading control. (C) Virus yields. Infected HeLa cells were harvested at 24 h p.i., and yields of ΔE3L mutant virus were determined by plaque titration on RK13 cells. The results shown are the means ± standard deviations determined from a minimum of three experiments.