Figure 5.

Segmented viruses package their genomes randomly or by using segment specific packaging signals. (a) Bunyavirus randomly package three genome segments, small (S), medium (M) and large (L), such that many progeny virions are empty or incomplete; (b) Influenza A virus package 8 genome segments selectively. Genome segments within budding virions are organized into a 1 + 7 arrangement with one central segment surrounded by seven others; (c) Influenza vRNAs are packaged as viral ribonucleoproteins (vRNPs). vRNAs are bound by nucleoprotein (NP) and a heterotrimeric polymerase. vRNA is incompletely coated by NP allowing for inter-segment vRNA-vRNA interactions to occur as a possible mechanism underlying the selective packaging process.