FIG. 2.

M protein and other inhibitors of host gene expression have similar effects on VSV-induced caspase-3 activation. HeLa cells (A) or BHK cells (B) were untreated (U), infected with rwt virus (rwt), infected with r-M51R-M virus (M51R), treated with actinomycin D (Act D), treated with DRB, infected with rM51R-M virus and treated with actinomycin D (M51R + Act D), or infected with rM51R-M virus and treated with DRB (M51R + DRB). HeLa cell lysates (A) were harvested at 12 h (open bars) and 18 h (solid bars), while BHK cell lysates (B) were harvested at 20 h (open bars) and 30 h (solid bars). Caspase-3-like activity was measured with a fluorogenic substrate. Protein concentrations were determined with a Lowry assay. The amount of caspase-3 activity is expressed in arbitrary fluorescence units per milligram of protein. The data represent the average ± standard deviation of three experiments.