title: Molecular mechanism of Reaper-Grim-Hid-mediated suppression of DIAP1-dependent Dronc ubiquitination.
abstract: The inhibitor of apoptosis protein DIAP1 inhibits Dronc-dependent cell death by ubiquitinating Dronc. The pro-death proteins Reaper, Hid and Grim (RHG) promote apoptosis by antagonizing DIAP1 function. Here we report the structural basis of Dronc recognition by DIAP1 as well as a novel mechanism by which the RHG proteins remove DIAP1-mediated downregulation of Dronc. Biochemical and structural analyses revealed that the second BIR (BIR2) domain of DIAP1 recognizes a 12-residue sequence in Dronc. This recognition is essential for DIAP1 binding to Dronc, and for targeting Dronc for ubiquitination. Notably, the Dronc-binding surface on BIR2 coincides with that required for binding to the N termini of the RHG proteins, which competitively eliminate DIAP1-mediated ubiquitination of Dronc. These observations reveal the molecular mechanisms of how DIAP1 recognizes Dronc, and more importantly, how the RHG proteins remove DIAP1-mediated ubiquitination of Dronc.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D020169:Caspases / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000201:enzymology; D051034:Inhibitor of Apoptosis Proteins; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000378:metabolism*; D010455:Peptides; D011485:Protein Binding; D025801:Ubiquitin / Q000378:metabolism
chemical_list: C111891:DIAP1 protein, Drosophila; D029721:Drosophila Proteins; C108880:HID protein, Drosophila; D051034:Inhibitor of Apoptosis Proteins; D009479:Neuropeptides; D010455:Peptides; D025801:Ubiquitin; C108881:grim protein, Drosophila; C086973:rpr protein, Drosophila; D020169:Caspases; C118731:dronc protein, Drosophila