Biochem J. 2009 Jan 1;417(1):149-60.

Ubiquitin binding modulates IAP antagonist-stimulated proteasomal degradation of c-IAP1 and c-IAP2(1).External

Blankenship, J. W., Varfolomeev, E., Goncharov, T., Fedorova, A. V., Kirkpatrick, D. S., Izrael-Tomasevic, A., Phu, L., Arnott, D., Aghajan, M., Zobel, K., Bazan, J. F., Fairbrother, W. J., Deshayes, K., Vucic, D.,
--- - Department of Protein Engineering, Genentech, Inc., 1 DNA Way, M/S 40, South San Francisco, CA 94080, USA.
A family of anti-apoptotic regulators known as IAP (inhibitor of apoptosis) proteins interact with multiple cellular partners and inhibit apoptosis induced by a variety of stimuli. c-IAP (cellular IAP) 1 and 2 are recruited to TNFR1 (tumour necrosis factor receptor 1)-associated signalling complexes, where they mediate receptor-induced NF-kappaB (nuclear factor kappaB) activation. Additionally, through their E3 ubiquitin ligase activities, c-IAP1 and c-IAP2 promote proteasomal degradation of NIK (NF-kappaB-inducing kinase) and regulate the non-canonical NF-kappaB pathway. In the present paper, we describe a novel ubiquitin-binding domain of IAPs. The UBA (ubiquitin-associated) domain of IAPs is located between the BIR (baculovirus IAP repeat) domains and the CARD (caspase activation and recruitment domain) or the RING (really interesting new gene) domain of c-IAP1 and c-IAP2 or XIAP (X-linked IAP) respectively. The c-IAP1 UBA domain binds mono-ubiquitin and Lys(48)- and Lys(63)-linked polyubiquitin chains with low-micromolar affinities as determined by surface plasmon resonance or isothermal titration calorimetry. NMR analysis of the c-IAP1 UBA domain-ubiquitin interaction reveals that this UBA domain binds the classical hydrophobic patch surrounding Ile(44) of ubiquitin. Mutations of critical amino acid residues in the highly conserved MGF (Met-Gly-Phe) binding loop of the UBA domain completely abrogate ubiquitin binding. These mutations in the UBA domain do not overtly affect the ubiquitin ligase activity of c-IAP1 or the participation of c-IAP1 and c-IAP2 in the TNFR1 signalling complex. Treatment of cells with IAP antagonists leads to proteasomal degradation of c-IAP1 and c-IAP2. Deletion or mutation of the UBA domain decreases this degradation, probably by diminishing the interaction of the c-IAPs with the proteasome. These results suggest that ubiquitin binding may be an important mechanism for rapid turnover of auto-ubiquitinated c-IAP1 and c-IAP2.
PMID: 18939944External
Arrow2 In vitro interaction Arrow2 In vivo interaction Arrow2 Characterization Arrow2 Functional role Arrow2 top
In vivo interaction
  Endogenous
expression
Overexpression DD1 DD2 Reference
Family DD1 DD2 Method Species Region Species Region
DD RIP Link TNFR1 Co-immunoprecipitation HT1080 18939944
DD TNFR1 Link TRADD Co-immunoprecipitation HT1080 18939944
(Link: click this icon to show interactions only between the two corresponding DDs)