Abstract
The interferon (IFN) system is a major effector of the innate immunity that allows time for the subsequent establishment of an adaptive immune response against a wide-range of pathogens. Their diverse biological actions are thought to be mediated by the products of specific but usually overlapping sets of cellular genes induced in the target cells. Ubiquitin ligase members of the tripartite motif (TRIM) protein family have emerged as IFN-induced proteins involved in both innate and adaptive immunity. In this report, we provide evidence that TRIM22 is a functional E3 ubiquitin ligase that is also ubiquitinated itself. We demonstrate that TRIM22 expression leads to a viral protection of HeLa cells against encephalomyocarditis virus infections. This effect is dependent upon its E3 ubiquitinating activity, since no antiviral effect was observed in cells expressing a TRIM22-deletion mutant defective in ubiquitinating activity. Consistent with this, TRIM22 interacts with the viral 3C protease (3C(PRO)) and mediates its ubiquitination. Altogether, our findings demonstrate that TRIM22 E3 ubiquitin ligase activity represents a new antiviral pathway induced by IFN against picornaviruses.