RNA structure interactions and ribonucleoprotein processes of the influenza A virus

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

The viral envelop is built from lipids derived from the host membrane and comprises the matrix protein 1 (M1; from Segment 7), which is located at the interface between the (Next frame) Transcription continues with the viral polymerase somehow dislodging the NP in its wake to obtain the mRNA transcript. Also depicted faintly are alternative splice factors from the spliceosome that can influence the resulting transcription. (Next frame) While the transcription process is happening, the vRNA and NP tend to recombine back to the rest state. (Final step) The poly-adenylation step is reached where further editing is required of the structure using the host RNA polymerase II system. It is important to remember that during this entire process, various mRNA packaging proteins are being recruited (e.g. the CBP. These are shown as a faint covering of the final mRNA. All this packaging is required for transport to the cytosol for translation into viral proteins. The schematic is inspired from [44] and [42] . The structure of the vRNP is based on the right-handed helix in [42] ; however, it is important to remember that [43] reports a left-handed helix. (A colour version of this figure is available online at: https://academic.oup.com/bfg) nucleocapsid and the lipid envelop. M1 is partly responsible for the curvature of the emerging viroid, supports the arrangement of the eight RNP on the inner surface of the lipid envelope and regulates the import and export of vRNPs into and out of the nucleus. Anchored to the viral envelope, with part of the peptide sequence occupying the border of the lipid and the nucleocapsid, extending through the lipid layer and jutting out from the surface, are two externally oriented glycoproteins: the hemmaglutinin (HA) and the NA. It is important to keep in mind that none of these envelop surface proteins are monomers. The HA forms a homotrimer (HA-trimer) that binds the sialylated glycans located on the surface of epithelial cells and initializes the process of fusion between viral envelope and the host's endosome. The NA forms a homotetramer (NA-tetramer) and appears to play a major role in the final steps of the budding process. In addition to these glycoproteins, matrix protein 2 (M2, Segment 7) is a small protein that combines into a homotetramer (M2-tetramer) serves as a transmembrane ion channel (a proton pump). HA and NA are the main antigens of IAV and are used to identify various subtypes of IAV, e.g. H3N2 specifies an IAV with the HA belonging to Subtype 3 and the NA also belonging to Subtype 2.