Virion-associated transcriptase activity of influenza recombinant and mutant strains.

A comparative study of the in vitro reaction kinetics of the virion RNA polymerase of influenza A strains WS and WSN was conducted to establish phenotypic differences for enzyme activity that might be exchanged as genetic markers among recombinants of these viruses. Characteristically, the RNA polymerase activity of WS virus showed an initial rate of synthesis about two- to threefold higher than that of WSN when assayed at 32 C. The two strains were also distinguishable by comparing the transcription rates of each strain at 32 and 37 C. The initial rate of WS was invariably higher at 37 than at 32 C, whereas the opposite was found with WSN. When a series of recombinants obtained from mixed infections with the WS and WSN viruses were examined for virion transcriptase activity, it was found that the two polymerase related markers behaved as properties which segregated independently of each other and of additional nonselective markers that were scored. Seven temperature-sensitive mutants of WSN virus representing distinct recombination-complementation groups were found to show a diminished transcriptase activity as compared to wild-type virus, and one of these clones (ts 24) was largely deficient for this function. None of these mutants appeared to possess a heat-liable virion polymerase.