JVI Accepts, published online ahead of print on 4 November 2009

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J. Virol. doi:10.1128/JVI.02006-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Host and viral translational mechanisms during Cricket paralysis virus infection

Julianne L. Garrey, Yun-Young Lee, Hilda H.T. Au, Martin Bushell, and Eric Jan^*

University of British Columbia, Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada; and School of Pharmacy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK

^* To whom correspondence should be addressed. Email: ej{at}interchange.ubc.ca.

The dicistrovirus is a positive-strand ssRNA virus which possesses two internal ribosome entry sites (IRES) that direct translation of distinct open reading frames encoding the viral structural and non-structural proteins. Through an unusual mechanism, the intergenic region (IGR) IRES responsible for viral structural protein expression mimics a tRNA to directly recruit the ribosome and set the ribosome into translational elongation. In this study, we explored the mechanism of host translational shutoff in Drosophila S2 cells infected by the dicistrovirus, Cricket paralysis virus (CrPV). CrPV infection of S2 cells results in host translational shutoff concomitant with an increase in viral protein synthesis. CrPV infection resulted in the dissociation of eIF4G and eIF4E early in infection and the induction of deIF2 phosphorylation at 3 hours post infection, which lags after the initial inhibition of host translation. Forced dephosphorylation of deIF2 by overexpression of dGADD34, which activates protein phosphatase I, did not prevent translational shutoff nor alter virus production, demonstrating that deIF2 phosphorylation is dispensable for host translational shutoff. However, premature induction of deIF2 phosphorylation by thapsigargin treatment early in infection reduced viral protein synthesis and replication. Finally, translation mediated by the 5' untranslated region (5'UTR) and the IGR IRESs were resistant to impairment of eIF4F or eIF2 in translation extracts. These results support a model by which the alteration of the deIF4F complex contribute to the shutoff of host translation during CrPV infection, thereby promoting viral protein synthesis via the CrPV 5'UTR and IGR IRESs.