Segment 8 of the influenza virus genome is unique in coding for two polypeptides.

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Abstract
It was shown previously that a 9th polypeptide with a MW of .apprxeq. 11,000 (NS2) found in influenza virus-infected cells was unique, that it could be synthesized in vitro, and that its expression in vivo required early protein synthesis. On the basis of these results it was suggested that one of the 8 genome RNA segments of influenza virus codes for 2 polypeptides. Differences in the electrophoretic mobility of the NS2 polypeptides of different strains of influenza A virus are described. These results provide further evidence that NS2 is virus coded and made possible genetic studies using recombinants between 2 virus strains (HK and PR8) whose NS2 polypeptides differ. These studies showed that the gene for NS2 reassorts with that of the nonstructural polypeptide NS1, which is coded by genome segment 8. A mRNA for NS2 was separated from that of NS1 and the other viral polypeptides by centrifugation and was translated in vitro. Hybridization of genome segment 8 to the total mRNA from infected cells specifically prevented the synthesis of NS2 and NS1. These results indicate that influenza virus genome segment 8 is transcribed into 2 separate mRNA that code for 2 polypeptides, NS1 and NS2. Possible mechanisms for the transcription of the 2 mRNA from either contiguous or overlapping genes are discussed.