title: Degradation of the encephalomyocarditis virus and hepatitis A virus 3C proteases by the ubiquitin/26S proteasome system in vivo.
abstract: We have isolated stably transfected mouse embryonic fibroblast cell lines that inducibly express either the mature encephalomyocarditis virus (EMCV) or hepatitis A virus (HAV) 3C protease and have used these cells to demonstrate that both proteins are subject to degradation in vivo by the ubiquitin/26S proteasome system. The detection of 3C protease expression in these cells requires inducing conditions and the presence of one of several proteasome inhibitors. Both 3C proteases are incorporated into conjugates with ubiquitin in vivo. HAV 3C protease expression has deleterious effects on cell viability, as determined by observation and counting of cells cultured in the absence or presence of inducing conditions. The EMCV 3C protease was found to be preferentially localized to the nucleus of induced cells, while the HAV 3C protease remains in the cytoplasm. The absence of polyubiquitinated EMCV 3C protease conjugates in nuclear fraction preparations suggests that localization to the nucleus can protect this protein from ubiquitination.
authors.affiliation: Department of Chemistry, Bates College, Lewiston, ME 04240, USA.
authors.forename: Peter E
authors.initials: PE
authors.lastname: Schlax
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Lewis
authors.forename: Antonio
authors.initials: A
authors.lastname: Planchart
authors.forename: T Glen
authors.initials: TG
authors.lastname: Lawson
mesh_terms: D000086042:3C Viral Proteases; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry; D002470:Cell Survival; D003546:Cysteine Endopeptidases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000737:chemistry; D004686:Encephalomyocarditis virus / Q000201:enzymology*; D005347:Fibroblasts / Q000821:virology; D030041:Hepatitis A virus / Q000201:enzymology*; D006801:Humans; D051379:Mice; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D025801:Ubiquitin / Q000378:metabolism; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D025801:Ubiquitin; D014764:Viral Proteins; D003546:Cysteine Endopeptidases; D000086042:3C Viral Proteases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease