Cardiovirus 2A protein associates with 40S but not 80S ribosome subunits during infection.

Host translation shutoff induced in picornavirus-infected cells is a well-known phenomenon. The mechanisms by which separate genera of the picornavirus family achieve this shutoff differ. This study examined alterations in the cellular translational components in HeLa cells infected with encephalomyocarditis virus (EMCV), a cardiovirus. In agreement with previous reports, EMCV induced a marked decrease in host mRNA translation. The inhibition correlated with the appearance of a significantly enhanced 80S peak in cells and a concomitant decrease in polysome abundance. Characterization of the 80S material revealed that these ribosomes were virtually devoid of mRNA. Viral protein 2A was tightly associated with some of the free 40S ribosome subunits, but it was not present in the 80S pool which accumulated after infection. Expression of 2A protein in cells in the absence infection was able to modulate the cellular translational environment to increase the ratio of internal ribosome entry site-dependent translation to cap-dependent translation of a reporter construct. The results provide further evidence for a role of 2A protein in the mechanism of cardiovirus-induced host translational shutoff.