Figure 4.

OpIAP and CpIAP block the processing of pro-Sf-caspase-1. Sf-21 cells transiently expressing pro-Sf-caspase-1 were infected with various viruses as indicated in each panel. Samples were collected at the times indicated and were subjected to immunoblot analysis. The presence of the C-terminal epitope tag allowed the detection of pro-Sf-caspase-1 and its processed p12 subunit. The identity of the p12 subunit was established based on its comigration with the product derived independently from plasmid expressing tagged p12 in Sf-21 cells (data not shown). The position of the size standards are shown on the left. The product seen below p12 (∗) is probably derived from cleavage after Asp-209 instead of Asp-195, the previously described (9) cleavage site from which the p12 subunit is derived. Lane 1 in A–H represents samples collected before virus infection.