Poliovirus proteinase 2A induces cleavage of eucaryotic initiation factor 4F polypeptide p220

Poliovirus infection of HeLa cells induces rapid shutoff of host protein synthesis, whereas translation of poliovirus RNA is not inhibited. It is presumed that shutoff is the result of proteolytic cleavage of component p220 of eucaryotic initiation factor 4F. To study whether poliovirus proteinase 2A is involved in this cleavage, we translated synthetic RNAs that contained the coding region for poliovirus-specific polypeptides P1 and 2A in vitro and assayed for cleavage of p220. We report here that cleavage of p220 occurred in all cases when active proteinase 2A was translated and that disruption of the coding sequence of 2A by linker insertion or deletion prevented processing of p220 in vitro. Activity of 2A was determined by its ability to cleave at the P1-P2 site of a segment of the poliovirus polyprotein. We also constructed a plasmid in which the 3'-most 500 nucleotides of the nontranslated region of encephalomyocarditis virus were linked to the coding sequence for poliovirus polypeptide 2A. Translation of the RNA transcript of this clone was very efficient and yielded a fusion protein that included 2A; this polypeptide also induced cleavage of p220. In vitro translation in the presence of antibodies against 2A specifically inhibited processing of p220, whereas incubation of in vitro translation products with antibodies against 2A after translation was completed did not prevent proteolysis of p220.