Functional interaction between Cydia pomonella granulovirus IAP proteins.

Cydia pomonella granulovirus (CpGV) encodes for three inhibitor of apoptosis (IAP) proteins. One of them, CpIAP3, was previously identified based on its capacity to substitute for the p35 gene in blocking Autographa californica nucleopolyhedrovirus (AcMNPV)-induced apoptosis in SF21 cells. In this paper, the function of the other two CpGV IAP proteins, Cp94 and CpIAP5, was studied. Neither Cp94 nor CpIAP5, independently or together, can block actinomycin D-induced apoptosis in transient expression experiments. However, CpIAP5 has a significant stimulatory effect on the ability of CpIAP3 to block apoptosis. The mechanism of this stimulation remains to be elucidated. This is the first evidence of functional interactions between IAPs encoded by a single baculovirus.