Selective packaging of the influenza A genome and consequences for genetic reassortment

• Direct base pairings between influenza A virus (IAV) viral RNAs (vRNAs) build up complex networks of interactions.
• Base pairing favors co-packaging of the interacting vRNAs.
• Viral ribonucleoproteins (vRNPs) are packaged as a supramolecular complex.
• The vRNA interaction networks are not conserved among viral strains.

Influenza A viruses package their segmented RNA genome in a selective manner. Electron tomography, biochemical assays, and replication assays of viruses produced by reverse genetics recently unveiled molecular details of this mechanism, whereby different influenza viral strains form different and unique networks of direct intermolecular RNA–RNA interactions. Together with detailed views of the three-dimensional structure of the viral ribonucleoparticles, these recent advances help us understand the rules that govern genome packaging. They also have deep implications for the genetic reassortment processes, which are responsible for devastating pandemics.