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IAPs contain an evolutionarily conserved ubiquitin-binding domain that regulates NF-κB as well as cell survival and oncogenesis


The covalent attachment of ubiquitin to target proteins influences various cellular processes, including DNA repair, NF-κB signalling and cell survival1. The most common mode of regulation by ubiquitin-conjugation involves specialized ubiquitin-binding proteins that bind to ubiquitylated proteins and link them to downstream biochemical processes. Unravelling how the ubiquitin-message is recognized is essential because aberrant ubiquitin-mediated signalling contributes to tumour formation2. Recent evidence indicates that inhibitor of apoptosis (IAP) proteins are frequently overexpressed in cancer and their expression level is implicated in contributing to tumorigenesis, chemoresistance, disease progression and poor patient-survival3. Here, we have identified an evolutionarily conserved ubiquitin-associated (UBA) domain in IAPs, which enables them to bind to Lys 63-linked polyubiquitin. We found that the UBA domain is essential for the oncogenic potential of cIAP1, to maintain endothelial cell survival and to protect cells from TNF-α-induced apoptosis. Moreover, the UBA domain is required for XIAP and cIAP2–MALT1 to activate NF-κB. Our data suggest that the UBA domain of cIAP2–MALT1 stimulates NF-κB signalling by binding to polyubiquitylated NEMO. Significantly, 98% of all cIAP2–MALT1 fusion proteins retain the UBA domain, suggesting that ubiquitin-binding contributes to the oncogenic potential of cIAP2–MALT1 in MALT lymphoma. Our data identify IAPs as ubiquitin-binding proteins that contribute to ubiquitin-mediated cell survival, NF-κB signalling and oncogenesis.

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Figure 1: IAPs carry an evolutionarily conserved UBA domain that mediates Ub binding.
Figure 2: RING-mediated dimerization of XIAP and cIAP1 is required for Ub binding.
Figure 3: The UBA is required for IAP function.
Figure 4: The ability of XIAP to induce NF-κB is dependent on its UBA domain.
Figure 5: The UBA domain of cIAP2–MALT1 interacts with polyubiquitylated NEMO.

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We would like to thank Xiaolu Yang, David Komander, David Barford, Thomas Farkas, Ivan Dikic and Marja Jaattela for reagents, discussions and invaluable technical support. We thank Irene Scarfò for help with the cIAP1 zebrafish experiments, and Hyejin Cho and Beicong Ma for excellent technical assistance and help with the mouse tumour model. We thank Alan Ashworth and members of the Meier laboratory for critical reading of the manuscript and helpful discussions. We thank Vishva Dixit for sharing unpublished results. M.G.-H. is supported by a fellowship from the Danish Cancer Society. M.M.S. is supported by a HFSP Career Developmental Award, Fondazione San Paolo and Regione Piemonte.

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Authors and Affiliations



M.G.-H. and M.D. performed all experiments, except for those in Fig. 4; M.M. and J.S. planned and performed the cIAP1−/− MEF reconstitution assay; M.M.S. planned and performed the zebrafish reconstitution assay; L.Z., W.X. and S.L. designed, performed and supervised the cIAP1 mouse tumour assay; T.T. provided various constructs and technical support; P.C.A.F. performed sequence alignments and database searches with structural prediction algorithms; J.M.B and M.Z. performed 3D modelling and sequence analysis; M.G.-H. and P.M. designed and supervised the study and wrote the paper.

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Correspondence to Mads Gyrd-Hansen or Pascal Meier.

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Gyrd-Hansen, M., Darding, M., Miasari, M. et al. IAPs contain an evolutionarily conserved ubiquitin-binding domain that regulates NF-κB as well as cell survival and oncogenesis. Nat Cell Biol 10, 1309–1317 (2008).

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