title: The TRC8 E3 ligase ubiquitinates MHC class I molecules before dislocation from the ER.
abstract: The US2 and US11 gene products of human cytomegalovirus promote viral evasion by hijacking the endoplasmic reticulum (ER)-associated degradation (ERAD) pathway. US2 and US11 initiate dislocation of newly translocated major histocompatibility complex class I (MHC I) from the ER to the cytosol for proteasome-mediated degradation, thereby decreasing cell surface MHC I. Despite being instrumental in elucidating the mammalian ERAD pathway, the responsible E3 ligase or ligases remain unknown. Using a functional small interfering RNA library screen, we now identify TRC8 (translocation in renal carcinoma, chromosome 8 gene), an ER-resident E3 ligase previously implicated as a hereditary kidney cancer gene, as required for US2-mediated MHC I ubiquitination. Depletion of TRC8 prevents MHC I ubiquitination and dislocation by US2 and restores cell surface MHC I. TRC8 forms an integral part of a novel multiprotein ER complex that contains MHC I, US2, and signal peptide peptidase. Our data show that the TRC8 E3 ligase is required for MHC I dislocation from the ER and identify a new complex associated with mammalian ERAD.
authors.affiliation: Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB20XY, England, UK.
authors.forename: Helen R
authors.initials: HR
authors.lastname: Stagg
authors.forename: Mair
authors.initials: M
authors.lastname: Thomas
authors.forename: Dick
authors.initials: D
authors.lastname: van den Boomen
authors.forename: Emmanuel J H J
authors.initials: EJ
authors.lastname: Wiertz
authors.forename: Harry A
authors.initials: HA
authors.lastname: Drabkin
authors.forename: Robert M
authors.initials: RM
authors.lastname: Gemmill
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Lehner
mesh_terms: D000818:Animals; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006367:HeLa Cells; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008285:Major Histocompatibility Complex; D009154:Mutation; D034622:RNA Interference; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D015395:Histocompatibility Antigens Class I; C114025:RNF139 protein, human; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; C118670:US2 protein, Varicellovirus; D025801:Ubiquitin; D014759:Viral Envelope Proteins