Background: Noroviruses use a virus-encoded protein, VPg, covalently linked to the viral RNA for translation.Results: The direct interaction of VPg with the central domain of eIF4G is required for norovirus translation.Conclusion: eIF4G plays a central role in norovirus VPg-dependent translation initiation.Significance: The VPg-eIF4G interaction may provide a suitable target for the specific inhibition of norovirus translation.

Murine norovirus (MNV), identified in 2003, is the only norovirus which replicates efficiently in tissue culture and as a result has been used extensively as a model for human noroviruses, a major cause of acute gastroenteritis. The current report describes the generation of a new approach to reverse genetics recovery of genetically defined MNV that relies on the transfection of in vitro transcribed capped RNA directly into cells. The use of the recently developed ScriptCap post-transcriptional enzymatic capping system, followed by optimized Neon mediated electroporation of the highly permissive RAW 264.7 cells, resulted in the rapid and robust recovery of infectious MNV. Transfection of cells capable of supporting virus replication but not permissive to virus infection, namely human or hamster kidney cells, also resulted in robust recovery of infectious virus without subsequent amplification by multiple rounds of re-infection. This latter system may provide a reproducible method to measure the specific infectivity of mutant norovirus RNA allowing the accurate quantitation of the effect of mutations on norovirus replication.

Highlights d A mechanism of hybrid gene birth is employed by many families of RNA viruses d Human RNA and viral RNA encode new genes together d Hybrid genes either make extensions of viral proteins or novel proteins (UFOs) d Human-virus genes and proteins play roles in pathogenesis and are conserved

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