EPSTEIN-BARR-VIRUS LATENT MEMBRANE PROTEIN-1 (LMP1) C-TERMINUS ACTIVATION REGION-2 (CTAR2) MAPS TO THE FAR C-TERMINUS AND REQUIRES OLIGOMERIZATION FOR NF-KAPPA-B ACTIVATION

The Epstein-Barr virus Latent Membrane Protein-1 (LMP1) has structural features and functions consistent with it being a constitutively acti ve cell surface receptor. The known association of LMP1 with members o f the TRAF family of proteins suggests that LMP1 transduces signals si milarly to the Tumour Necrosis Factor Receptor (TNFR) family of cell s urface receptors that signal by forming dimers or trimers in response to binding of extracellular ligands. However, interactions between LMP 1 and the TRAFs have so far only been described for the C-terminal act ivation region 1 (CTAR1) of LMP1 and no direct interactions of the TRA Fs with the second NF-kappa B activation domain (CTAR2) have been repo rted. We have now mapped the NF-kappa B activation domain of CTAR2 to a highly conserved stretch of 6 amino acids at the far C-terminus (cod ons 379 to 384 in B95.8 LMP1). In addition, we constructed chimeric re ceptor molecules which contain the ligand-binding extracellular domain and the transmembrane domain of rat CD2 fused to the C-terminus of LM P1 encoding the CTAR1 and/or the CTAR2 domain. Interestingly, the func tion of a chimera encoding CTAR2 alone, as well as the function of a c himera encoding both CTAR1 and CTAR2 was found to be inducible upon an tibody-mediated crosslinking. These inducible chimeric proteins also a llowed us to demonstrate that LMP1 mediated NF-kappa B activation is a n immediate event following activation of LMP1.