Gene name | RNA strand (segment number) | Function(s) of protein encoded by this gene |
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PB2 (polymerase basic 2) | 1 | A subunit of viral RNA polymerase involved in cleaving the cap structure of host cell mRNA and generating primers that are subverted for use in the synthesis of viral RNA. |
PB1 (polymerase basic 1) | 2 | Core subunit of viral RNA polymerase. Required for polymerase assembly. |
PB1-F2 | 2 | Binds to components of the host mitochondria, sensitising the cell to apoptosis and contributing to pathogenicity. |
PA (polymerase acidic) | 3 | A subunit of viral RNA polymerase which also has protease activity of unknown function. |
HA (haemagglutinin) | 4 | Antigenic glycoprotein used for binding to (infecting) the host cell. |
NP (nucleoprotein) | 5 | RNase resistant protein. Binds viral genomic RNA to form stable ribonucleoproteins and targets these for export from the host nucleus into the cytosol. Also involved in viral genome packaging and viral assembly. |
NA (neuraminidase) | 6 | Cleaves sialic acid. Important for releasing viral particles from host cell. |
M1 (matrix 1) | 7 | Binds viral genomic RNA and forms a coat inside the viral envelope in virions. Inside the host cell, it starts forming a layer under patches of the membrane rich in viral HA, NA, and M2 and so facilitates viral assembly and budding from the host cell. |
M2 (matrix 2) | 7 | Transmembrane ion channel protein. Allows protons into the virus capsid, acidifying the interior, destabilising binding of M1 to the viral genomic RNA which leads to uncoating of the viral particle inside the host cell. |
NS1 (non-structural 1) | 8 | Inhibits nuclear export of the host’s own mRNA, thereby giving preference to viral genomic RNA. Blocks the expression of some host inflammatory mediators (interferons) and interferes with T cell activation*. |
NS2/NEP (non-structural 2/ nuclear export protein) | 8 | Mediates the export of viral genomic RNA from the host nucleus to the cytoplasm. |