FIG 6.

The decrease in virus production is not due to infected Rb knockdown cells undergoing apoptosis. (A) Serum-starved scrambled control cells (Scr) or Rb knockdown cells (Rb2) were infected at an MOI of 1 and treated with DMSO or pan-caspase inhibitor Z-VAD-FMK at the time of infection and replenished at 48 h postinfection. Combined cell-free and cell-associated virus was collected 4 days postinfection, and the titers of virus were determined by standard plaque assay. The data are mean titers ± the standard deviations from six biological replicates. The statistical significance was determined by a permutation test (*, P < 0.02; n.s., P > 0.45). (B) Protein lysates from equal numbers of serum-starved scrambled control cells (Scr) or Rb knockdown cells (Rb2) mock infected or infected at an MOI of 1 for 6 or 72 h were analyzed with the indicated antibodies by Western blotting. (C) Serum-starved scrambled control cells (Scr) or Rb knockdown cells (Rb2) were infected at an MOI of 1, and 72 h later the cell viability was determined by trypan blue exclusion. At least 80 cells were counted per replicate, and the bars represent the mean percentages of live cells ± the standard deviations of three biological replicates. Statistical significance was assayed by using the Student t test (n.s., P > 0.17).