Mapping of the influenza virus genome II. Identification of the P1, P2, and P3 genes

Polyacrylamide gel electrophoresis of the RNAs of influenza A viruses was performed under conditions in which each of the eight RNA segments of influenza A/PR/8/34 (H0N1) virus migrates differently from the equivalent segments of influenza A/Hong Kong/8/68 (H3N2) virus. As reported previously [Palese, P. and Schulman, J. L. Proc. Nat. Acad. Sci. USA 73, 2142–2146 (1976)] , analysis of RNA patterns of recombinant viruses derived from these two parents permitted the identification of the fourth RNA segment (the slowest-moving RNA segment is counted as #1) of each virus as the gene coding for hemagglutinin, and the fifth segment of Hong Kong virus and the sixth segment of PR8 virus as the genes for the respective neuraminidases. Three more genes have been identified by correlating migration patterns of RNAs with protein patterns of recombinant viruses on gradient polyacrylamide gels. The slowest-moving band (RNA 1) is the gene coding for the third largest influenza virus protein (P3). RNA segment 2 codes for the largest protein (Pl), and the P2 protein is coded for by RNA segment 3.