Nature Cell Biology5, 467 - 473 (2003)
Published online: 14 April 2003; | doi:10.1038/ncb984
Degradation of DIAP1 by the N-end rule pathway is essential for regulating apoptosis
Mark Ditzel1, 3, Rebecca Wilson1, 3, Tencho Tenev1, Anna Zachariou1, Angela Paul2, Emma Deas1
& Pascal Meier1
1
The Breakthrough Toby Robins Breast Cancer Research Centre, Institute of Cancer Research, Mary-Jean Mitchell Green Building, Chester Beatty Laboratories, Fulham Road, London SW3 6JB, UK
2
Cell and Molecular Biology, Institute of Cancer Research, Chester Beatty Laboratories, Fulham Road, London SW3 6JB, UK
3
These authors contributed equally to this work
Correspondence should be addressed to Pascal Meier pmeier@icr.ac.uk
Some members of the inhibitor of apoptosis (IAP) protein family block apoptosis by binding to and neutralizing active caspases. We recently demonstrated that a physical association between IAP and caspases alone is insufficient to regulate caspases in vivo and that an additional level of control is provided by IAP-mediated ubiquitination of both itself and the associated caspases1. Here we show that Drosophila IAP 1 (DIAP1) is degraded by the 'N-end rule' pathway and that this process is indispensable for regulating apoptosis. Caspase-mediated cleavage of DIAP1 at position 20 converts the more stable pro-N-degron of DIAP1 into the highly unstable, Asn-bearing, DIAP1 N-degron of the N-end rule degradation pathway. Thus, DIAP1 represents the first known metazoan substrate of the N-end rule pathway that is targeted for degradation through its amino-terminal Asn residue. We demonstrate that the N-end rule pathway is required for regulation of apoptosis induced by Reaper and Hid expression in the Drosophila melanogaster eye. Our data suggest that DIAP1 instability, mediated through caspase activity and subsequent exposure of the N-end rule pathway, is essential for suppression of apoptosis. We suggest that DIAP1 safeguards cell viability through the coordinated mutual destruction of itself and associated active caspases.
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