Requirements for the selective degradation of endoplasmic reticulum-resident major histocompatibility complex class I proteins by the viral immune evasion molecule mK3

Xiaoli Wang, Rose Connors, Michael R. Harris, Ted H. Hansen, Lonnie Lybarger

Research output: Contribution to journalArticle

28 Scopus citations


Recent studies suggest that certain viral proteins co-opt endoplasmic reticulum (ER) degradation pathways to prevent the surface display of major histocompatibility complex class I molecules to the immune system. A novel example of such a molecule is the mK3 protein of gammaherpesvirus 68. mK3 belongs to an extensive family of structurally similar viral and cellular proteins that function as ubiquitin ligases using a conserved RING-CH domain. In the specific case of mK3, it selectively targets the rapid degradation of nascent class I heavy chains in the ER while they are associated with the class I peptide-loading complex (PLC). We present here evidence that the PLC imposes a relative proximity and/or orientation on the RING-CH domain of mK3 that is required for it to specifically target class I molecules for degradation. Furthermore, we demonstrate that full assembly of class I molecules with peptide is not a prerequisite for mK3-mediated degradation. Surprisingly, although the cytosolic tail of class I is required for rapid mK3-mediated degradation, we observed that a class I mutant lacking lysine residues in its cytosolic tail was ubiquitinated and degraded in the presence of mK3 in a manner indistinguishable from wild-type class I molecules. These findings are consistent with a "partial dislocation" model for turnover of ER proteins and define some common features of ER degradation pathways initiated by structurally distinct herpesvirus proteins.

Original languageEnglish (US)
Pages (from-to)4099-4108
Number of pages10
JournalJournal of Virology
Issue number7
Publication statusPublished - Apr 2005


ASJC Scopus subject areas

  • Immunology

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