The 5′-untranslated tripartite leader sequences present in all viral mRNAs processed from major late transcripts, which enhance translation during the late phase of infection, reduce or eliminate the requirement for the cap-binding complex e1F-4F. This property of the tripartite leader sequence is believed to contribute to the selective translation of viral mRNAs in infected cells, because the cap-binding protein is underphosphorylated, with concomitant inhibition of the activity of e1F-4F.