MUTATIONAL ANALYSIS OF INFLUENZA-VIRUS PROMOTER ELEMENTS IN-VIVO

RNA polymerase I transcription in vivo in transiently DNA-transfected cells has been used to express influenza virus vRNA molecules coding f or chloramphenicol acetyltransferase (CAT) in an antisense orientation . Influenza virus superinfection provided viral RNA polymerase and oth er proteins required for transcriptional conversion of minus-strand vR NA into plus-strand viral mRNA molecules expressing CAT activity. This system has been used for analysis of the vRNA sequences which coopera tively constitute the vRNA promoter structure via nucleotide exchanges as well as deletions and insertions of both terminal segments. Severa l mutants caused greatly enhanced expression over wild-type levels, wh ich was transmitted during serial passage of progeny virus. The data o btained for the mutations in various promoter elements support a model implicating double-stranded vRNA promoter structures in binding of vi ral polymerase, and in consecutive steps during initiation of RNA synt hesis.