FIG. 4.

Using nonsense-mediated mRNA decay to determine if RSV packages previously translated RNA genomes. (A) If RSV packages RNAs that are translated, the NMD effect (degradation of PTC-containing RNA) should be seen both in the cell and in progeny virions. (B) Segregation into two populations means that certain unspliced RNAs are specific for translating viral proteins while others are specific for encapsidation. Since the RNAs are restricted to either the translation or the packaging activities, the NMD effect should be seen only in the cellular RNAs. Virion RNAs would be unaffected by PTCs since translation would not take place.