Mechanism of Dronc activation in Drosophila cells.

Proteolytic processing is required for the activation of most caspases. However, recent reports have suggested that the activation of the mammalian initiator caspase caspase-9 occurs during dimerization rather than after processing. Previously, we reported that, in normal living Drosophila S2 cells, the initiator caspase Dronc is continuously processed to a 40 kDa form we called Pr1 and that, during apoptosis, a second processed form of 37 kDa is also observed, which we called Pr2.

Ubiquitin protein ligase activity of the anti-apoptotic baculovirus protein Op-IAP3.

The baculovirus inhibitor of apoptosis protein (IAP) Op-IAP3 is required to prevent apoptosis during infection of insect cells by Orgyia pseudotsugata M nucleopolyhedrovirus (OpMNPV) and inhibits apoptosis when overexpressed in insect and mammalian cells. Although previous reports have demonstrated that the RING domain is important for the anti-apoptotic function of Op-IAP3, the function of this domain in Op-IAP3 has not been studied. Here, the ability of Op-IAP3 to function as an E3 ubiquitin protein ligase was examined.