title: Regulation of the Drosophila ubiquitin ligase DIAP1 is mediated via several distinct ubiquitin system pathways.
abstract: Inhibitors of apoptosis proteins (IAPs) suppress cell death by inactivating proapoptotic regulators, and therefore play important roles in controlling apoptosis in normal and malignant cells. Many IAPs are ubiquitin ligases, and their activity is mediated via ubiquitination and subsequent degradation of their targets. Here we corroborate a previous observation that DIAP1 (Drosophila IAP1) can be degraded via a two-step mechanism: (i) limited caspase-mediated cleavage and (ii) degradation of the released fragment via the ubiquitin N-end rule pathway. Yet, we demonstrate that this pathway is not the only one involved in DIAP1 degradation, and the intact protein can be degraded independent of prior caspase cleavage. Importantly, this mode of degradation does not require the RING-finger-mediated autoubiquitinating activity of DIAP1, believed to target many RING-finger E3s for self-destruction. Our preliminary data suggest that DIAP2 mediates DIAP1 degradation, suggesting a novel regulatory loop within the apoptotic pathway. Studying the role of the autoubiquitinating activity of DIAP1, we demonstrate that it does not involve formation of Lys48-based polyubiquitin chains, but probably chains linked via Lys63. Our preliminary data suggest that the autoubiquitination serves to attenuate the ligase activity of DIAP1 towards its exogenous substrates.
authors.affiliation: Cancer and Vascular Biology Research Center, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel.
authors.forename: Y
authors.initials: Y
authors.lastname: Herman-Bachinsky
authors.forename: H-D
authors.initials: HD
authors.lastname: Ryoo
authors.forename: A
authors.initials: A
authors.lastname: Ciechanover
authors.forename: H
authors.initials: H
authors.lastname: Gonen
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D004330:Drosophila; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D016296:Mutagenesis; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D014176:Protein Biosynthesis / Q000502:physiology; D034622:RNA Interference; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D016335:Zinc Fingers
chemical_list: C111891:DIAP1 protein, Drosophila; C111892:DIAP2 protein, Drosophila; D029721:Drosophila Proteins; D051034:Inhibitor of Apoptosis Proteins; D010455:Peptides; D011994:Recombinant Proteins; D025801:Ubiquitin; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases; D020169:Caspases