RNA polymerase of influenza virus. I. Comparison of the virion-associated RNA polymerase activity of various strains of influenza virus.

A systematic and comparative study was performed on the polypeptide composition and the RNA polymerase activity associated with virions of various strains of influenza A virus, including four human and two avian viruses. Significant differences were found in the molecular weights of not only hemagglutinin (HA) but also both nucleoprotein (NP) and membrane protein (M), as determined by polyacrylamide gel electrophoresis under denaturing conditions. The results indicate that, among viruses sharing the same serotype determined by the surface proteins HA and NA (neuraminidase), considerable variations exist in the structure of viral proteins, including inner proteins. The relative contents of viral proteins also varied among these strains grown under similar conditions. The total content of three P proteins, the putative RNA polymerase subunits, was within the range between 1.1 and 2.2% of total viral proteins and roughly paralleled the virion-associated RNA polymerase activity. The virion-associated RNA polymerase of all the strains tested were stimulated by the same dinucleotide primers, ApG or GpG, indicating that the specificity of transcription initiation is conserved among wide varieties of influenza virus.