RNA structure interactions and ribonucleoprotein processes of the influenza A virus

Dawson, Wayne K; Lazniewski, Michal; Plewczynski, Dariusz

Each of the eight segments is individually packaged into a structurally distinct vRNP particle. A cartoon of a typical vRNP is shown in Figure 1 (top panel). The medium-gray/green beads represent the NP (Segment 5 in Table 1) , where a polymer of NP molecules forms a scaffold consisting of a right-handed doublestranded (ds) helix of NPs in an ensiform (needle-like) structure [42] [43] [44] . The single-stranded vRNA sequence is represented by the light-gray/cyan lines (on the 5 0 half of the sequence) that connects adjacent NP beads together and similarly the blackish/ navy-blue lines (on the 3 0 half). Thus, the vRNA sequence is left partially exposed as it winds around the NP-scaffolding; as though the NP forms a lining for the vRNA. The NP-scaffold does not play a significant role in protecting the vRNA because the NPlined vRNA can be cut by ribonucleases [42] . The only part of the vRNA sequence where any dsRNA base pairing occurs is the highly conserved 12 and 13 nucleotide (nt) sequence on the 5 0and 3 0 -most ends of the vRNA segment, respectively [45] . Likewise, the NP-lined vRNA complex also appears to strongly restrict the formation of RNA secondary structure, though the last section of this review will discuss an emerging nuanced view.