Regulated production of an influenza virus spliced mRNA mediated by virus-specific products.

The influenza virus NS2 mRNA is generated through processing by cellular enzymes of a transcript (the NS1 mRNA) of virion RNA segment 8. Production of this mRNA is altered in cells infected with a mutant of influenza A (fowl plague) virus. The proportion of segment 8 transcripts which accumulated in a spliced form was found to be considerably lower in mutant virus-infected cells than in cells infected with wild-type virus, and the amplification in production of NS2 mRNA relative to that of the NS1 mRNA, which normally occurs during infection with wild-type virus, was not observed with the mutant. The NS1 mRNA specified by the mutant virus has unaltered splice recognition sites and was apparently processed normally during a mixed infection with a strain of virus which is wild-type for production of NS2 mRNA. These results suggest that the production of NS2 mRNA is regulated by virus-specific products; these products may act by increasing the efficiency of splicing of NS1 mRNA.