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.