Temporal control for translation of influenza virus mRNAs.

cDNAs for genome RNAs of influenza virus A/PR/8/34 were cloned and portions containing the ATG initiation codon for translation were inserted into the 5' leader sequence of the chloramphenicol acetyltransferase (CAT) gene in a pSV2cat vector. In cells that were transfected with a plasmid containing a cDNA segment for the early gene and then super-infected with influenza virus, the maximal CAT activity was obtained at the early stage of infection. In contrast, a plasmid containing a cDNA segment for the late gene directed the highest activity at the late stage of infection. These observations together with the previous observations [K. Yamanaka et al. (1988) Virus Genes 2: 19-30] indicate that the translational efficiency of influenza viral mRNA is subjected to temporal control following viral infection.