A high-coverage shRNA screen identifies TMEM129 as an E3 ligase involved in ER-associated protein degradation

Van de Weijer ML, Bassik MC, Luteijn RD, Voorburg CM, Lohuis MA, Kremmer E, Hoeben RC, LeProust EM, Chen S, Hoelen H, Ressing ME, Patena W, Weissman JS, McManus MT, Wiertz EJ, Lebbink RJ

Nature Communcations

May 08, 2014

Misfolded ER proteins are retrotranslocated into the cytosol for degradation via the ubiquitin-proteasome system. The human cytomegalovirus protein US11 exploits this ER-associated protein degradation (ERAD) pathway to downregulate HLA class I molecules in virus-infected cells, thereby evading elimination by cytotoxic T-lymphocytes. US11-mediated degradation of HLA class I has been instrumental in the identification of key components of mammalian ERAD, including Derlin-1, p97, VIMP and SEL1L. Despite this, the process governing retrotranslocation of the substrate is still poorly understood. Here using a high-coverage genome-wide shRNA library, we identify the uncharacterized protein TMEM129 and the ubiquitin-conjugating E2 enzyme UBE2J2 to be essential for US11-mediated HLA class I downregulation. TMEM129 is an unconventional C4C4-type RING finger E3 ubiquitin ligase that resides within a complex containing various other ERAD components, including Derlin-1, Derlin-2, VIMP and p97, indicating that TMEM129 is an integral part of the ER-resident dislocation complex mediating US11-induced HLA class I degradation. (Publication Abstract)

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