The inhibitors of apoptosis of Epiphyas postvittana nucleopolyhedrovirus

In this study, four inhibitor of apoptosis genes (iaps) in the genome of Ep iphyas postvittana nucleopolyhedrovirus (EppoMNPV) that are homologous to i ap-1, iap-2, iap-3 and iop-4 genes of other baculoviruses have been identif ied. All four iap genes were sequenced and the iap-1 and iap-2 genes were s hown to be functional inhibitors of apoptosis, The icrp-l, iap-2 and iap-3 genes contain two baculovirus apoptosis inhibitor repeat motifs and a C3HC4 RING finger-like motif, The activity of the iap genes was tested by transi ent expression in Spodoptera frugiperda (Sf-21) cells treated with the apop tosis-inducing agents actinomycin D, cycloheximide, anisomycin, tumour necr osis factor-a and UV light. The iap-2 gene prevented apoptosis induced by a ll agents tested, indicating activity towards a conserved component(s) of m ultiple apoptotic pathways. However, the iap-2 gene was unable to function in the absence of a gene immediately upstream of iap-2 that has homology to the orf69 gene of Autographa californica MNPV, The use of a CMV promoter r escued the apoptosis inhibition activity of the iap-a gene, indicating that the upstream orf69 homologue is associated with expression of iap-a, The i ap-1 gene was able to delay the onset of apoptosis caused by all of the ind uction agents tested but, unlike iap-2, was unable to prevent the developme nt of an apoptotic response upon prolonged exposure of cells to the apoptos is induction agents. No anti-apoptotic activity was observed for the iap-3 and iap-4 genes of EppoMNPV.