The ubiquitin-proteasome system facilitates the transfer of murine coronavirus from endosome to cytoplasm during virus entry.

The ubiquitin-proteasome system is involved in cellular endocytosis and maturation of some viruses. In this study, we found that proteasome inhibitors blocked mouse hepatitis virus replication at an early step in the viral life cycle. In the presence of MG132, the entering viruses accumulated in both the endosome and denser lysosome, suggesting that the ubiquitin-proteasome system is involved in the release of virus from the endosome to the cytosol during the virus entry step.