Structure and replication of echovirus type 12. 2. Viral polypeptides synthesized in the infected cell

A technique has been devised which allows us to label predominantly echovirus-12-specific proteins: upon infection in the presence of D-(--)-2-(alpha-hydroxybenzyl)benzimidazole plus actinomycin D the shut-off of host-cell protein synthesis takes place as in infected, untreated cells, but the bulk of viral protein synthesis is inhibited. Upon removal of 2-(alpha-hydroxybenzyl)benzimidazole a peak of viral protein synthesis is visible 3 h later. The time course of appearance of viral proteins is followed by dodecyl sulfate/polyacrylamide gel electrophoresis of the proteins which had been pulse-labeled at different times post-infection. The protein patterns induced in the infected cells by echovirus 12 and poliovirus 2 are compared; though they are different, some analogies are observed. The molecular weights of the polypeptides are determined. In the presence of amino acid analogs cleavage of viral proteins is impaired. A group of large proteins up to Mr 220,000 is detectable in the infected cell which ordinarily is not observed. The 220,000-Mr protein may represent the translation product of the total viral RNA. The hierarchy of the virus-specific proteins originating from post-translational cleavage is discussed.