Transient bicistronic vRNA segments for indirect selection of recombinant influenza viruses

The 5'- and 3'-terminal regions of influenza vRNA molecules are known to constitute the promoter structure upon association with viral RNA polymerase in an activated complementary conformation. An inherent requirement for their location at the very ends of the vRNA molecules always has been implied because of that natural structure, but this study demonstrates that one or both of the promoter sequences may be relocated into vRNA-internal positions and still retain their polymerase-binding function. External extensions of vRNA molecules employed include either single-stranded RNA sequences