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Mol. Cell. Biol., Dec 1996, 7098-7108, Vol 16, No. 12
O Devergne, E Hatzivassiliou, KM Izumi, KM Kaye, MF Kleijnen, E Kieff and G Mosialos
The Epstein-Barr virus (EBV) transforming protein LMP1 appears to be a
constitutively activated tumor necrosis factor receptor (TNFR) on the basis
of an intrinsic ability to aggregate in the plasma membrane and an
association of its cytoplasmic carboxyl terminus (CT) with TNFR- associated
factors (TRAFs). We now show that in EBV-transformed B lymphocytes most of
TRAF1 or TRAF3 and 5% of TRAF2 are associated with LMP1 and that most of
LMP1 is associated with TRAF1 or TRAF3. TRAF1, TRAF2, and TRAF3 bind to a
single site in the LMP1 CT corresponding to amino acids (aa) 199 to 214,
within a domain which is important for B- lymphocyte growth transformation
(aa 187 to 231). Further deletional and alanine mutagenesis analyses and
comparison with TRAF binding sequences in CD40, in CD30, and in the LMP1 of
other lymphycryptoviruses provide the first evidence that PXQXT/S is a core
TRAF binding motif. The negative effects of point mutations in the
LMP1(1-231) core TRAF binding motif on TRAF binding and NF-kappaB
activation genetically link the TRAFs to LMP1(1-231)-mediated NF-kappaB
activation. NF-kappaB activation by LMP1(1-231) is likely to be mediated by
TRAF1/TRAF2 heteroaggregates since TRAF1 is unique among the TRAFs in
coactivating NF-kappaB with LMP1(1-231), a TRAF2 dominant- negative mutant
can block LMP1(1-231)-mediated NF-kappaB activation as well as TRAF1
coactivation, and 30% of TRAF2 is associated with TRAF1 in EBV-transformed
B cells. TRAF3 is a negative modulator of LMP1(1- 231)-mediated NF-kappaB
activation. Surprisingly, TRAF1, -2, or -3 does not interact with the
terminal LMP1 CT aa 333 to 386 which can independently mediate NF-kappaB
activation. The constitutive association of TRAFs with LMP1 through the aa
187 to 231 domain which is important in NF-kappaB activation and primary
B-lymphocyte growth transformation implicates TRAF aggregation in LMP1
signaling.
Copyright © 1996, American Society for Microbiology
Association of TRAF1, TRAF2, and TRAF3 with an Epstein-Barr virus LMP1 domain important for B-lymphocyte transformation: role in NF-kappaB activation
Department of Microbiology, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
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