Interaction of tumor necrosis factor receptor-associated factors with the latent membrane protein 1 is essential for activation of NF-κB

The Epstein-Barr virus latent membrane protein 1 (LMP1) oncoprotein causes multiple cellular changes, including activation of the NF-kappaB transcription factor. To elucidate its possible mechanism, the interaction between LMP1 and the tumor necrosis factor receptor associated factor (TRAF) molecules was detected by the immunoprecipitation-Western blotting assay. Results showed that LMP1 was co-precipitated with TRAF1, 2, 3 in the LMP1-HNE2 cell line. In the meantime, kappaB reporter gene analysis revealed that over expression of TRAF1 or TRAF2 augmented LMP1-mediated NF-kappaB activation from LMP1, suprisingly, overexpression of either TRAF3 or an dominant negative TRAF3 inhibited the NF-kappaB activation, indicating that TRAF1 or TRAF2 is a positive modulator of LMP1-mediated NF-kappaB activation, whereas, TRAF3 is a negative modulator. Rather both CTAR1 (carboxy-terminal activating region 1) and CTAR2 domains of LMP1 can independently activate NF-kappaB by interacting with TRAF proteins. These data indicate that LMP1 interacts TRAF1, 2, 3 which are important for LMP1-mediated NF-kappaB activation, and further suggest that signaling from TRAFs may be involved in the progression to malignancy in cells of epithelial origin such as nasopharyngeal carcinoma (NPC).