JGV logo Journal of General Virology
First posted online 4 August 2000 ARTICLE ABSTRACT
Rec 17 April 2000; Acc 27 July 2000 DOI: 10.1099/vir.0.17098-0

The inhibitors of apoptosis of Epiphyas postvittana nucleopolyhedrovirus

Terry Maguire, Penelope Harrison, Otto Hyink, James Kalmakoff and Vernon K. Ward

Department of Microbiology, School of Medical Sciences, University of Otago, PO Box 56, Dunedin, New Zealand

In this study, four inhibitor of apoptosis genes (iaps) in the genome of Epiphyas postvittana nucleopolyhedrovirus (EppoMNPV) that are homologous to iap-1, iap-2, iap-3 and iap-4 genes of other baculoviruses have been identified. All four iap genes were sequenced and the iap-1 and iap-2 genes were shown to be functional inhibitors of apoptosis. The iap-1, 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 transient expression in Spodoptera frugiperda (Sf-21) cells treated with the apoptosis-inducing agents actinomycin D, cycloheximide, anisomycin, tumour necrosis factor-alpha and UV light. The iap-2 gene prevented apoptosis induced by all agents tested, indicating activity towards a conserved component(s) of multiple 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 rescued the apoptosis inhibition activity of the iap-2 gene, indicating that the upstream orf69 homologue is associated with expression of iap-2. The iap-1 gene was able to delay the onset of apoptosis caused by all of the induction agents tested but, unlike iap-2, was unable to prevent the development of an apoptotic response upon prolonged exposure of cells to the apoptosis induction agents. No anti-apoptotic activity was observed for the iap-3 and iap-4 genes of EppoMNPV.

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© 2000 SGM

This article is now available in the November 2000 print issue of JGV (vol. 81, 2803–2811). The complete issue of the journal may be seen in electronic form on JGV Online.