Synthesis of the NS 2 nonstructural protein messenger RNA of influenza A viruses occurs in the absence of viral protein synthesis.

The NS 2 messenger RNA (mRNA) of several influenza A viruses was shown to be synthesized in primary transcription. Analysis of in vitro translation products of mRNAs from infected MDCK cells treated with cycloheximide indicated that the NS 2 mRNA in addition to the NS 1 mRNA was synthesized with PR/8, Udorn, and Aichi viruses. The findings indicated that the NS 1 mRNA of these viruses was able to be spliced into the NS 2 mRNA as a primary transcript without viral protein synthesis, although the extent of splicing varied among different virus strains.