Structure and synthesis of influenza virus complementary RNAs

Two classes of genome transcript are involved in the replication of influenza viruses, both of which contain molecules complementary to all eight genome RNAs. One of these classes, which comprises the viral mRNAs, consists of transcripts that have additional 5' terminal non-viral sequences including "cap" structures and 3' terminal polyadenylate sequences but which lack sequences corresponding to nucleotides 1-16 at the 5' termini of the virus RNAs. The members of the other class are complete genome transcripts with no additional sequences and these are thought to be the templates for genome replication. The syntheses of the two classes of molecules have a number of distinctive features which together with their structural properties indicate that they are synthesized by different mechanisms.