The Inhibitor of Apoptosis Protein Fusion c-IAP2·MALT1 Stimulates NF-κB Activation Independently of TRAF1 AND TRAF2

Abstract

The inhibitors of apoptosis (IAPs) are a family of cell death inhibitors found in viruses and metazoans. All members of the IAP family have at least one baculovirus IAP repeat (BIR) motif that is essential for their anti-apoptotic activity. The t(11, 18)(q21;q21) translocation fuses the BIR domains of c-IAP2 with the paracaspase/MALT1 (mucosa-associated lymphoid tissue) protein, a critical mediator of T cell receptor-stimulated activation of NF-κB. The c-IAP2·MALT1 fusion protein constitutively activates the NF-κB pathway, and this is considered critical to malignant B cell transformation and lymphoma progression. The BIR domains of c-IAP1 and c-IAP2 interact with tumor necrosis factor receptor-associated factors 1 and 2 (TRAF1 and TRAF2). Here we investigated the importance of TRAF1 and TRAF2 for c-IAP2·MALT1-stimulated NF-κB activation. We identified a novel epitope within the BIR1 domains of c-IAP1 and c-IAP2 that is crucial for their physical interaction with TRAF1 and TRAF2. The c-IAP2·MALT1 fusion protein associates with TRAF1 and TRAF2 using the same binding site. We explored the functional relevance of this interaction and established that binding to TRAF1 and TRAF2 is not required for c-IAP2·MALT1-stimulated NF-κB activation. Furthermore, gene ablation of TRAF2 or combined down-regulation of TRAF1 and TRAF2 did not affect c-IAP2·MALT1-stimulated signaling. However, TRAF1/2-binding mutants of c-IAP2·MALT1 still oligomerize and activate NF-κB, suggesting that oligomerization might be important for signaling of the fusion protein. Therefore, the t(11, 18)(q21;q21) translocation creating the c-IAP2·MALT1 fusion protein activates NF-κB and contributes to human malignancy in the absence of signaling adaptors that might otherwise regulate its activity. The inhibitors of apoptosis (IAPs) are a family of cell death inhibitors found in viruses and metazoans. All members of the IAP family have at least one baculovirus IAP repeat (BIR) motif that is essential for their anti-apoptotic activity. The t(11, 18)(q21;q21) translocation fuses the BIR domains of c-IAP2 with the paracaspase/MALT1 (mucosa-associated lymphoid tissue) protein, a critical mediator of T cell receptor-stimulated activation of NF-κB. The c-IAP2·MALT1 fusion protein constitutively activates the NF-κB pathway, and this is considered critical to malignant B cell transformation and lymphoma progression. The BIR domains of c-IAP1 and c-IAP2 interact with tumor necrosis factor receptor-associated factors 1 and 2 (TRAF1 and TRAF2). Here we investigated the importance of TRAF1 and TRAF2 for c-IAP2·MALT1-stimulated NF-κB activation. We identified a novel epitope within the BIR1 domains of c-IAP1 and c-IAP2 that is crucial for their physical interaction with TRAF1 and TRAF2. The c-IAP2·MALT1 fusion protein associates with TRAF1 and TRAF2 using the same binding site. We explored the functional relevance of this interaction and established that binding to TRAF1 and TRAF2 is not required for c-IAP2·MALT1-stimulated NF-κB activation. Furthermore, gene ablation of TRAF2 or combined down-regulation of TRAF1 and TRAF2 did not affect c-IAP2·MALT1-stimulated signaling. However, TRAF1/2-binding mutants of c-IAP2·MALT1 still oligomerize and activate NF-κB, suggesting that oligomerization might be important for signaling of the fusion protein. Therefore, the t(11, 18)(q21;q21) translocation creating the c-IAP2·MALT1 fusion protein activates NF-κB and contributes to human malignancy in the absence of signaling adaptors that might otherwise regulate its activity. A family of anti-apoptotic regulators known as inhibitor of apoptosis (IAP) 2The abbreviations used are: IAP, inhibitor of apoptosis; c-IAP, cellular IAP; XIAP, X-chromosome linked IAP; ML-IAP, melanoma IAP; BIR, baculovirus IAP repeat; TNF, tumor necrosis factor; TRAF, TNF receptor-associated factor; NF-κB, nuclear factor-κB; SMAC, second mitochondrial activator of caspases; MEF, mouse embryonic fibroblast; CARD, caspase-associated recruitment domain; HA, hemagglutinin; MALT, mucosa-associated lymphoid tissue. 2The abbreviations used are: IAP, inhibitor of apoptosis; c-IAP, cellular IAP; XIAP, X-chromosome linked IAP; ML-IAP, melanoma IAP; BIR, baculovirus IAP repeat; TNF, tumor necrosis factor; TRAF, TNF receptor-associated factor; NF-κB, nuclear factor-κB; SMAC, second mitochondrial activator of caspases; MEF, mouse embryonic fibroblast; CARD, caspase-associated recruitment domain; HA, hemagglutinin; MALT, mucosa-associated lymphoid tissue. proteins was initially identified and functionally described in baculoviruses, and IAP protein homologues are now known in both invertebrates and vertebrates (1Salvesen G.S. Abrams J.M. Oncogene. 2004; 23: 2774-2784Crossref PubMed Scopus (212) Google Scholar). IAP proteins can interact directly with a variety of inducers and effectors of apoptosis and block apoptosis induced by diverse stimuli (2Salvesen G.S. Duckett C.S. Nat Rev Mol. Cell. Biol. 2002; 3: 401-410Crossref PubMed Scopus (1569) Google Scholar). This places IAP proteins in a central position as inhibitors of death signals that proceed through a number of different pathways (3Miller L.K. Trends Cell Biol. 1999; 9: 323-328Abstract Full Text Full Text PDF PubMed Scopus (316) Google Scholar). Members of the IAP family are characterized by the presence of at least one and, most commonly in humans, three tandem baculovirus IAP repeat (BIR) domains (3Miller L.K. Trends Cell Biol. 1999; 9: 323-328Abstract Full Text Full Text PDF PubMed Scopus (316) Google Scholar). In addition, most IAP proteins possess a carboxyl-terminal RING finger motif involved in ubiquitination (4Vaux D.L. Silke J. Nat Rev Mol. 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A. 1996; 93: 13973-13978Crossref PubMed Scopus (365) Google Scholar, 9Wang C.Y. Mayo M.W. Korneluk R.G. Goeddel D.V. Baldwin Jr., A.S. Science. 1998; 281: 1680-1683Crossref PubMed Scopus (2566) Google Scholar). c-IAPs and TRAF2 associate through their BIR and TRAF-N domains (7Rothe M. Pan M.G. Henzel W.J. Ayres T.M. Goeddel D.V. Cell. 1995; 83: 1243-1252Abstract Full Text PDF PubMed Scopus (1053) Google Scholar), and recent studies indicate that the BIR1 domain of c-IAP1 and c-IAP2 is critical for that interaction (10Tang E.D. Wang C.Y. Xiong Y. Guan K.L. J. Biol. Chem. 2003; 278: 37297-37305Abstract Full Text Full Text PDF PubMed Scopus (183) Google Scholar, 11Samuel T. Welsh K. Lober T. Togo S.H. Zapata J.M. Reed J.C. J. Biol. Chem. 2006; 281: 1080-1090Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar). c-IAP1 and c-IAP2 are also RING finger-containing ubiquitin ligases capable of promoting ubiquitination and proteasomal degradation of TRAF1, TRAF2, and several of their binding partners (4Vaux D.L. Silke J. Nat Rev Mol. Cell. Biol. 2005; 6: 287-297Crossref PubMed Scopus (526) Google Scholar, 12Lee J.S. Hong U.S. Lee T.H. Yoon S.K. Yoon J.B. Proteomics. 2004; 4: 3376-3382Crossref PubMed Scopus (24) Google Scholar, 13Hu S. Du M.Q. Park S.M. Alcivar A. Qu L. Gupta S. Tang J. Baens M. Ye H. Lee T.H. Marynen P. Riley J.L. Yang X. J. Clin. Investig. 2006; 116: 174-181Crossref PubMed Scopus (89) Google Scholar). Interestingly, the t(11, 18)(q21;q21) genetic translocation fuses the BIR domains of c-IAP2 with the central and carboxyl-terminal portions of paracaspase/MALT1 (14Akagi T. Motegi M. Tamura A. Suzuki R. Hosokawa Y. Suzuki H. Ota H. Nakamura S. Morishima Y. Taniwaki M. Seto M. Oncogene. 1999; 18: 5785-5794Crossref PubMed Scopus (297) Google Scholar, 15Dierlamm J. Baens M. Wlodarska I. Stefanova-Ouzounova M. Hernandez J.M. Hossfeld D.K. De Wolf-Peeters C. Hagemeijer A. Van den Berghe H. Marynen P. Blood. 1999; 93: 3601-3609Crossref PubMed Google Scholar, 16Morgan J.A. Yin Y. Borowsky A.D. Kuo F. Nourmand N. Koontz J.I. Reynolds C. Soreng L. Griffin C.A. Graeme-Cook F. Harris N.L. Weisenburger D. Pinkus G.S. Fletcher J.A. Sklar J. Cancer Res. 1999; 59: 6205-6213PubMed Google Scholar). This translocation is the most frequent chromosomal aberration associated with MALT lymphoma (17Ye H. Liu H. Attygalle A. Wotherspoon A.C. Nicholson A.G. Charlotte F. Leblond V. Speight P. Goodlad J. Lavergne-Slove A. Martin-Subero J.I. Siebert R. Dogan A. Isaacson P.G. Du M.Q. Blood. 2003; 102: 1012-1018Crossref PubMed Scopus (299) Google Scholar). MALT lymphoma is the most common extranodal non-Hodgkin lymphoma, arising from a background of chronic inflammation and autoimmune disease (18Isaacson P.G. Best Pract. Res. Clin. Haematol. 2005; 18: 57-68Crossref PubMed Scopus (111) Google Scholar). The c-IAP2·MALT1 fusion protein constitutively activates the NF-κB pathway, which is potentially seminal for development of inflammation-associated tumors (19Karin M. Cao Y. Greten F.R. Li Z.W. Nat. Rev. Cancer. 2002; 2: 301-310Crossref PubMed Scopus (2242) Google Scholar, 20Lucas P.C. Yonezumi M. Inohara N. McAllister-Lucas L.M. Abazeed M.E. Chen F.F. Yamaoka S. Seto M. Nunez G. J. Biol. Chem. 2001; 276: 19012-19019Abstract Full Text Full Text PDF PubMed Scopus (377) Google Scholar, 21Uren A.G. O'Rourke K. Aravind L.A. Pisabarro M.T. Seshagiri S. Koonin E.V. Dixit V.M. Mol. Cell. 2000; 6: 961-967Abstract Full Text Full Text PDF PubMed Google Scholar). However, c-IAP2 and MALT1 independently do not possess the same activation capacity (20Lucas P.C. Yonezumi M. Inohara N. McAllister-Lucas L.M. Abazeed M.E. Chen F.F. Yamaoka S. Seto M. Nunez G. J. Biol. Chem. 2001; 276: 19012-19019Abstract Full Text Full Text PDF PubMed Scopus (377) Google Scholar, 21Uren A.G. O'Rourke K. Aravind L.A. Pisabarro M.T. Seshagiri S. Koonin E.V. Dixit V.M. Mol. Cell. 2000; 6: 961-967Abstract Full Text Full Text PDF PubMed Google Scholar). MALT1, also known as paracaspase, contains a death domain, two immunoglobulin-like domains (Ig-like), a region homologous to caspases, and a globular domain. Despite having a caspase-like region, MALT1 does not have any protease activity (22Snipas S.J. Wildfang E. Nazif T. Christensen L. Boatright K.M. Bogyo M. Stennicke H.R. Salvesen G.S. Biol. Chem. 2004; 385: 1093-1098Crossref PubMed Scopus (31) Google Scholar). Instead, it mediates antigen receptor-stimulated NF-κB activation by ubiquitinating NF-κB essential modulator (NEMO) (23Zhou H. Wertz I. O'Rourke K. Ultsch M. Seshagiri S. Eby M. Xiao W. Dixit V.M. Nature. 2004; 427: 167-171Crossref PubMed Scopus (449) Google Scholar, 24Zhou H. Du M.Q. Dixit V.M. Cancer Cell. 2005; 7: 425-431Abstract Full Text Full Text PDF PubMed Scopus (128) Google Scholar). The c-IAP2·MALT1 protein appears to stimulate NF-κB signaling through self-oligomerization that deregulates the ubiquitin ligase activity of MALT1 (24Zhou H. Du M.Q. Dixit V.M. Cancer Cell. 2005; 7: 425-431Abstract Full Text Full Text PDF PubMed Scopus (128) Google Scholar). A report by Zhou et al. (24Zhou H. Du M.Q. Dixit V.M. Cancer Cell. 2005; 7: 425-431Abstract Full Text Full Text PDF PubMed Scopus (128) Google Scholar) demonstrated that the BIR1 domain of c-IAP2 is critical for c-IAP2·MALT1-induced NF-κB activation. In the present study, we investigated the importance of TRAF1 and TRAF2 for c-IAP2·MALT1-stimulated NF-κB activation. We identified a novel epitope within the BIR1 domain, comprising residues in the first α-helix of c-IAP1 and c-IAP2, that is critical for the physical interaction with TRAF1 and TRAF2. The importance of these residues is highlighted in binding studies with endogenous TRAF proteins. Finally, we established that binding to TRAF1 and TRAF2 is not required for c-IAP2·MALT1-stimulated NF-κB activation. These results suggest that, despite binding TRAF1 and TRAF2 through the BIR1 domain of c-IAP2, the c-IAP2·MALT1 fusion activates NF-κB through oligomerization. Expression Constructs—Plasmids expressing FLAG-ML-IAP, Myc-SMAC, TRAF1-FLAG, TRAF2-Myc, HA-c-IAP2·MALT1 (case2), FLAG-case2, and HA-case2 deletions have been described previously (21Uren A.G. O'Rourke K. Aravind L.A. Pisabarro M.T. Seshagiri S. Koonin E.V. Dixit V.M. Mol. Cell. 2000; 6: 961-967Abstract Full Text Full Text PDF PubMed Google Scholar, 24Zhou H. Du M.Q. Dixit V.M. Cancer Cell. 2005; 7: 425-431Abstract Full Text Full Text PDF PubMed Scopus (128) Google Scholar, 25Vucic D. Deshayes K. Ackerly H. Pisabarro M.T. Kadkhodayan S. Fairbrother W.J. Dixit V.M. J. Biol. Chem. 2002; 277: 12275-12279Abstract Full Text Full Text PDF PubMed Scopus (137) Google Scholar, 26McCarthy J.V. Ni J. Dixit V.M. J. Biol. Chem. 1998; 273: 16968-16975Abstract Full Text Full Text PDF PubMed Scopus (361) Google Scholar). The breakpoint for c-IAP2 is nucleotide 2048, and for paracaspase/MALT1, it is nucleotide 814 in genetic fusion (14Akagi T. Motegi M. Tamura A. Suzuki R. Hosokawa Y. Suzuki H. Ota H. Nakamura S. Morishima Y. Taniwaki M. Seto M. Oncogene. 1999; 18: 5785-5794Crossref PubMed Scopus (297) Google Scholar, 15Dierlamm J. Baens M. Wlodarska I. Stefanova-Ouzounova M. Hernandez J.M. Hossfeld D.K. De Wolf-Peeters C. Hagemeijer A. Van den Berghe H. Marynen P. Blood. 1999; 93: 3601-3609Crossref PubMed Google Scholar, 16Morgan J.A. Yin Y. Borowsky A.D. Kuo F. Nourmand N. Koontz J.I. Reynolds C. Soreng L. Griffin C.A. Graeme-Cook F. Harris N.L. Weisenburger D. Pinkus G.S. Fletcher J.A. Sklar J. Cancer Res. 1999; 59: 6205-6213PubMed Google Scholar). XIAP, and c-IAP2, as as deletions and of c-IAP1 and c-IAP2, were by and the mutants in c-IAP2, and were using a Cell and embryonic human and mouse embryonic were using E. H. D. D. M. D. A. J. Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). and were by and were using and The used were and to BIR1 of c-IAP1 were in using the BIR1 domain as were as described previously D. Deshayes K. Ackerly H. Pisabarro M.T. Kadkhodayan S. Fairbrother W.J. Dixit V.M. J. Biol. Chem. 2002; 277: 12275-12279Abstract Full Text Full Text PDF PubMed Scopus (137) Google Scholar, D. Stennicke H.R. Pisabarro M.T. Salvesen G.S. Dixit V.M. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). and were using of the c-IAP1 BIR1 domain was using the of and using the of J. S.J. Li P. S.M. R. Y. Mol. Cell. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar) and Kadkhodayan S. Ackerly H. D. J.A. G. D. D. Deshayes K. Fairbrother W.J. 2003; PubMed Scopus Google Scholar) as The was using the as in NF-κB and were with the NF-κB activity was at the of using the as described previously (23Zhou H. Wertz I. O'Rourke K. Ultsch M. Seshagiri S. Eby M. Xiao W. Dixit V.M. Nature. 2004; 427: 167-171Crossref PubMed Scopus (449) Google Scholar, 24Zhou H. Du M.Q. Dixit V.M. Cancer Cell. 2005; 7: 425-431Abstract Full Text Full Text PDF PubMed Scopus (128) Google Scholar). of were by using the and at The were used for gene TRAF1, and TRAF2, and and were as described previously E. H. D. D. M. D. A. J. Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). The of the BIR1 of c-IAP1 and c-IAP2 for been to associate with c-IAP1 and c-IAP2 not with (7Rothe M. Pan M.G. Henzel W.J. Ayres T.M. Goeddel D.V. Cell. 1995; 83: 1243-1252Abstract Full Text PDF PubMed Scopus (1053) Google Scholar, A.G. M. K.L. D.L. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: PubMed Scopus Google Scholar). the of this we TRAF2 with c-IAP2, XIAP, and c-IAP1 and c-IAP2 TRAF2, interaction was or and TRAF2 the of c-IAP1 and c-IAP2 for TRAF2 we BIR domains and finger of c-IAP1 and c-IAP2 both c-IAP1 and c-IAP2, the BIR1 domain associated with TRAF2, the and finger did not and of XIAP, ML-IAP, and the BIR domains of c-IAP1 and c-IAP2 were by binding to not the region within the BIR1 domain of c-IAP1 and c-IAP2 for interaction with TRAF2, we and portions of the BIR1 domain with portions of the domain of BIR domains of IAP proteins two by three and three at the carboxyl-terminal of the domain We that the three or the first two and three or the first two BIR1 and of c-IAP1 of the three in a that still with TRAF2, of the first two did not This that the of the BIR1 domain might be critical for the interaction with TRAF2. this we the first α-helix of the BIR1 domain with the region of the domain from c-IAP1 This protein to TRAF2, in the of c-IAP1 protein or as BIR1 domain and not of the first α-helix of the BIR1 domain and IAP proteins a motif several residues to c-IAP1 and c-IAP2 that are not present in or We these residues with and found that binding to TRAF2 A recent report by et al. T. Welsh K. Lober T. Togo S.H. Zapata J.M. Reed J.C. J. Biol. Chem. 2006; 281: 1080-1090Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar) that of residues and at the of the second α-helix of the BIR1 domain is required for TRAF2 mutants with we of c-IAP1 and c-IAP2 with the of the residues with of the two residues in and with or a of We the ability of these to endogenous TRAF2 protein from and found that both of as as their to TRAF2 of mutants was by of these proteins by c-IAP1 not of the BIR1 domain of c-IAP1 that the residues are the of the BIR domain, to or within and and are at the of to the residues identified in the Therefore, we have identified a novel binding for TRAF2 the BIR1 domain of c-IAPs that a and that the previously described binding site. c-IAP2·MALT1-stimulated NF-κB BIR1 domain of c-IAP2 been as critical for c-IAP2·MALT1-induced NF-κB activation (24Zhou H. Du M.Q. Dixit V.M. Cancer Cell. 2005; 7: 425-431Abstract Full Text Full Text PDF PubMed Scopus (128) Google Scholar). we identified the BIR1 domain as a crucial region for binding TRAF2, we investigated the importance of TRAF2 for c-IAP2·MALT1-induced NF-κB activation. et al. T. Welsh K. Lober T. Togo S.H. Zapata J.M. Reed J.C. J. Biol. Chem. 2006; 281: 1080-1090Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar) in their report that TRAF2, by of its binding to the BIR1 domain of c-IAP2, might be required for NF-κB activation by that we BIR of the c-IAP2·MALT1 fusion protein to as for binding to TRAF2 demonstrated that the BIR1 domain of is required for binding of or endogenous TRAF2 B and the importance of the identified residues in the first and second of the BIR1 domain, we the and for TRAF2 of or in endogenous TRAF2, the importance of residues for TRAF2 binding by as as by the c-IAPs the of TRAF2 binding in NF-κB we the mutants of and their ability to activate gene with NF-κB activity at with the previously (21Uren A.G. O'Rourke K. Aravind L.A. Pisabarro M.T. Seshagiri S. Koonin E.V. Dixit V.M. Mol. Cell. 2000; 6: 961-967Abstract Full Text Full Text PDF PubMed Google Scholar, 24Zhou H. Du M.Q. Dixit V.M. Cancer Cell. 2005; 7: 425-431Abstract Full Text Full Text PDF PubMed Scopus (128) Google Scholar), a BIR1 of or c-IAP2 or MALT1 did not activate NF-κB This that a BIR1 physical interaction with TRAF2 is not required for NF-κB activation. that TRAF2 is not required in NF-κB we mutants for their ability to activate NF-κB in or mutants of and NF-κB in both and and These indicate that TRAF2 is not required for NF-κB activation. c-IAP1 and c-IAP2 with TRAF1 in a to to TRAF2, c-IAP1 and c-IAP2 also interact with TRAF1 (7Rothe M. Pan M.G. Henzel W.J. Ayres T.M. Goeddel D.V. Cell. 1995; 83: 1243-1252Abstract Full Text PDF PubMed Scopus (1053) Google Scholar, A.G. M. K.L. D.L. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: PubMed Scopus Google Scholar). in the BIR1 domain of affect with TRAF1, we TRAF1 with BIR domain deletions and of and for with TRAF2, associated with TRAF1 through the BIR1 domain of its c-IAP2 and in the first and in the second α-helix of the BIR1 domain that interaction We with endogenous TRAF1 and the importance of the residues at the of the BIR1 domain Finally, we the same in the of c-IAP1 and demonstrated that they binding to endogenous TRAF1 We used and ML-IAP, IAP proteins that do not interact with as to the of this TRAF1 and TRAF2 associate with c-IAP1 and c-IAP2 in a by binding to a comprising residues within the first two of the BIR1 domain. of TRAF1 and TRAF2 NF-κB the of TRAF1 and TRAF2 in NF-κB we used to these two or in of TRAF1 or TRAF2 or of both did not NF-κB activation by we have in the a of to these two still NF-κB in their absence A and Finally, we the mutants of affect the oligomerization of the BIR1 domain of c-IAP2 been as crucial for oligomerization of (24Zhou H. Du M.Q. Dixit V.M. Cancer Cell. 2005; 7: 425-431Abstract Full Text Full Text PDF PubMed Scopus (128) Google Scholar). the in α-helix 1 or the two in α-helix 2 or the of with at with we that oligomerization does not to be a physical interaction with TRAF1 or TRAF2. IAP proteins interact with a variety of inducers and effectors of and the IAP the BIR most of However, with the of SMAC, most IAP proteins and their BIR domains have binding XIAP, for is a and inhibitor of and are c-IAP1 and c-IAP2 IAP of their they associate with TRAF1 and TRAF2. We have investigated the importance of the BIR domains of c-IAPs for TRAF1 and binding and have found the BIR1 domain to be both and for this of the TRAF2 the domain and have to the of a motif Ye H. C. D. H. Cell. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar, V. L. H. Nature. 1999; PubMed Scopus Google Scholar). However, TRAF2 associates with c-IAPs the TRAF-N domain that the region (7Rothe M. Pan M.G. Henzel W.J. Ayres T.M. Goeddel D.V. Cell. 1995; 83: 1243-1252Abstract Full Text PDF PubMed Scopus (1053) Google Scholar). The TRAF-N domain not been and are known that of binding the interaction and we and different portions of the BIR1 domain for We found that residues to and within the first α-helix are critical for the These residues a novel interaction for TRAF1 and the BIR1 domains of the c-IAPs that is and for Interestingly, these in with two previously identified residues at the of a the of the BIR1 domain. This the the potentially binding for and the where a the domain a binding for the of Kadkhodayan S. Ackerly H. D. J.A. G. D. D. Deshayes K. Fairbrother W.J. 2003; PubMed Scopus Google Scholar, C. T. J. J.C. Nature. 2000; PubMed Scopus Google Scholar, G. J. Du C. Wang X. Y. Nature. 2000; PubMed Scopus Google Scholar, D. K. H. Kadkhodayan S. Deshayes K. Salvesen G.S. Fairbrother W.J. Biochem. J. 2005; 385: PubMed Scopus Google Scholar). studies of the interaction the BIR1 domain and the TRAF-N domain the of interaction of these proteins. The most common chromosomal translocation associated with MALT lymphoma, t(11, a fusion protein the BIR domains of c-IAP2 and the caspase-like and of The BIR1 domain of to be critical for NF-κB activation and is also essential for the interaction with TRAF2. Therefore, we and T. Welsh K. Lober T. Togo S.H. Zapata J.M. Reed J.C. J. Biol. Chem. 2006; 281: 1080-1090Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar) have that TRAF2 might be crucial for NF-κB by as for NF-κB activation or as oligomerization for In of this a TRAF2 NF-κB activation in studies (21Uren A.G. O'Rourke K. Aravind L.A. Pisabarro M.T. Seshagiri S. Koonin E.V. Dixit V.M. Mol. Cell. 2000; 6: 961-967Abstract Full Text Full Text PDF PubMed Google Scholar). TRAF that been in NF-κB L. L. Chen Mol. Cell. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar), does not to be important for this signaling (24Zhou H. Du M.Q. Dixit V.M. Cancer Cell. 2005; 7: 425-431Abstract Full Text Full Text PDF PubMed Scopus (128) Google Scholar). However, in and down-regulation of TRAF2 that TRAF2 does not a in NF-κB activation. We have also investigated the that TRAF, TRAF1, mediates NF-κB activation. TRAF1 does not have a RING finger and activate NF-κB its (6Rothe M. Wong S.C. Henzel W.J. Goeddel D.V. Cell. 1994; 78: 681-692Abstract Full Text PDF PubMed Scopus (929) Google Scholar). it directly the BIR domains of c-IAPs (7Rothe M. Pan M.G. Henzel W.J. Ayres T.M. Goeddel D.V. Cell. 1995; 83: 1243-1252Abstract Full Text PDF PubMed Scopus (1053) Google Scholar), it and their oligomerization. However, as with TRAF2, of TRAF1 binding or down-regulation of TRAF1 NF-κB activation. Therefore, TRAF1 and TRAF2 do not to be involved in NF-κB activation. mutants that the ability to associate with TRAF1 and TRAF2 still activate NF-κB and can still suggesting that TRAF1 and TRAF2 do not a in this of NF-κB that the chromosomal translocation that the c-IAP2·MALT1 fusion protein can activate NF-κB and to human malignancy in the absence of signaling adaptors that might otherwise regulate its activity. We and for members of the and for and the and for