Expression of poliovirus 2Apro in mammalian cells: effects on translation.

Poliovirus protease 2Apro has been efficiently expressed in HeLa and COS cells upon transfection with vector pTM1-2A and infection with the recombinant vaccinia virus bearing the T7 RNA polymerase. The expressed poliovirus protease localizes to the cytoplasm of the transfected cells, both in the endoplasmic reticulum and in vesicles scattered in the cytoplasm. Cleavage of p220, a component of initiation factor eIF-4F, selectively occurs from 5 h post-infection in transfected cells infected with the recombinant virus. This cleavage correlates in time with the profound inhibition observed in the synthesis of vaccinia virus proteins. A similar blockade of vesicular stomatitis virus translation takes place upon 2Apro expression. Finally, the synthesis of poliovirus protein 2C from a recombinant vaccinia virus that expresses this protein under the EMC untranslated leader region is not affected by the synthesis of 2Apro. These findings lend support to the idea that translation of capped mRNAs requires the integrity of p220, while this requirement is not observed when translation of a mRNA bearing a picornavirus leader region is assayed.