Selective Genome Packaging Mechanisms of Influenza A Viruses

The genome of influenza A virus (IAV) comprises eight segmented, single-stranded, negative-sense RNAs. The genome packaging mechanism of IAV was a long-standing enigma, but it is now widely accepted that IAV packages one copy of each of the eight viral RNA (vRNA) segments in a selective manner. Accumulating evidence over the last decade suggests that the eight unique vRNAs are selected via intersegment interactions mediated by their segment-specific genome packaging signals; however, the characteristics of these RNA-based interactions largely remain unknown. This review summarizes our current knowledge of IAV selective genome packaging and the possible mechanisms underlying the selection of the eight unique vRNAs.