Identification of Transmembrane Protein 134 as a Novel LMP1- Binding Protein by Using Bimolecular Fluorescence Complementation and an Enhanced Retroviral Mutagen

Latent membrane protein 1 (LMP1) of Epstein-Barr virus induces constitutive signaling in infected cells. LMP1 signaling re-quires oligomerization of LMP1 via its transmembrane domain, localization to lipid rafts in the membrane, and association of the LMP1 cytoplasmic domain to adaptor proteins, such as the tumor necrosis factor receptor-associated factors (TRAFs). Pro-tein complementation is a novel technique to examine protein-protein interaction through the assembly of functional fluores-cent proteins or enzymes from inactive fragments. A previous study in our lab demonstrated the use of bimolecular fluorescence complementation (BiFC) to study the assembly of the LMP1 signaling complexes within the plasmamembrane of mammalian cells. In the present study, LMP1 was used as bait in a genome-wide BiFC screen with an enhanced retroviral mutagen to identify new LMP1-binding proteins. Our screen identified a novel LMP1-binding protein, transmembrane protein 134 (Tmem134). Tmem134 is a candidate oncogene that is amplified in breast cancer cell lines. Binding, colocalization, and cofractionation be-tween LMP1 and Tmem134 were confirmed. Finally, Tmem134 affected LMP1-induced NF-B induction. Together, these data suggest that BiFC is a unique and novel platform to identify proteins recruited to the LMP1-signaling complex. Epstein-Barr virus (EBV) is a large double-stranded DNA virusthat is classified as a gamma-1 herpesvirus of the lymphocryp-tovirus genus (26, 40). EBV has infected greater than 90 % of the world’s population and is the etiologic agent of infectious mono-nucleosis (7, 20). EBV was the first virus to be associated wit