Epstein-Barr virus latent membrane protein 1 activation of NF-κB through IRAK1 and TRAF6

Epstein-Barr virus latent membrane protein 1 (LMP1) activation of NF-kappaB is critical for Epstein-Barr virus-infected B lymphocyte survival. LMP1 activates the IkappaB kinase complex and NF-kappaB through two cytoplasmic signaling domains that engage tumor necrosis factor receptor-associated factor (TRAF)1/2/3/5 or TRADD and RIP. We now use cells lacking expression of TRAF2, TRAF5, TRAF6, IKKalpha, IKKbeta, IKKgamma, TAB2, IL-1 receptor-associated kinase (IRAK)1, or IRAK4 to assess their roles in LMP1-mediated NF-kappaB activation. LMP1-induced ReIA nuclear translocation was similar in IKKa knockout (KO) and WT murine embryo fibroblasts (MEFs) but substantially deficient in IKKbeta KO MEFs. NF-kappaB-dependent promoter responses were also substantially deficient in IKKbeta KO MEFs but were hyperactive in IKKa KO MEFs. More surprisingly, NIF-kappaB responses were near normal in TRAF2 and TRAF5 double-KO MEFs, IKKgamma KO MEFs,TAB2 KO MEFs,and IRAK4 KO MEFs but were highly deficient in TRAM KO MEFs and IRAK1 KO HEK293 cells. Consistent with the importance of TRAF6, LMP1-induced NF-kappaB activation in HEK293 cells was inhibited by expression of dominant-negative TAB2 and Ubc13 alleles. These data extend a role for IKKa in IKKbeta regulation, identify an unusual IKKbeta-clepenclent and IKKgamma-independent NF-kappaB activation, and indicate that IRAK1 and TRAF6 are essential for LMP1-induced NF-kappaB activation.