title: FBXW7 Facilitates Nonhomologous End-Joining via K63-Linked Polyubiquitylation of XRCC4.
abstract: FBXW7 is a haploinsufficient tumor suppressor with loss-of-function mutations occurring in human cancers. FBXW7 inactivation causes genomic instability, but the mechanism remains elusive. Here we show that FBXW7 facilitates nonhomologous end-joining (NHEJ) repair and that FBXW7 depletion causes radiosensitization. In response to ionizing radiation, ATM phosphorylates FBXW7 at serine 26 to recruit it to DNA double-strand break (DSB) sites, whereas activated DNA-PKcs phosphorylates XRCC4 at serines 325/326, which promotes binding of XRCC4 to FBXW7. SCF(FBXW7) E3 ligase then promotes polyubiquitylation of XRCC4 at lysine 296 via lysine 63 linkage for enhanced association with the Ku70/80 complex to facilitate NHEJ repair. Consistent with these findings, a small-molecule inhibitor that abrogates XRCC4 polyubiquitylation reduces NHEJ repair. Our study demonstrates one mechanism by which FBXW7 contributes to genome integrity and implies that inactivated FBXW7 in human cancers could be a strategy for increasing the efficacy of radiotherapy.
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: David
authors.initials: D
authors.lastname: Karnak
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Mingjia
authors.initials: M
authors.lastname: Tan
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Theodore S
authors.initials: TS
authors.lastname: Lawrence
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA. Electronic address: mmccrack@med.umich.edu.
authors.forename: Meredith A
authors.initials: MA
authors.lastname: Morgan
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA; Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, 310029, Zhejiang, China; Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, 310003, Zhejiang, China. Electronic address: sunyi@umich.edu.
authors.forename: Yi
authors.initials: Y
authors.lastname: Sun
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D003517:Cyclopentanes / Q000494:pharmacology; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair / Q000528:radiation effects; D051747:DNA-Activated Protein Kinase / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism*; D000073979:F-Box-WD Repeat-Containing Protein 7; D045325:HCT116 Cells; D006801:Humans; D008239:Lysine; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy; D010766:Phosphorylation; D025821:Polyubiquitin / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000528:radiation effects; D011743:Pyrimidines / Q000494:pharmacology; D034622:RNA Interference; D011836:Radiation Tolerance; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D044764:Ubiquitin-Activating Enzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D014452:Ubiquitins / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D003517:Cyclopentanes; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D044783:F-Box Proteins; D000073979:F-Box-WD Repeat-Containing Protein 7; C513273:FBXW7 protein, human; C513272:Fbxw7 protein, mouse; D009687:Nuclear Proteins; D011743:Pyrimidines; D011838:Radiation-Sensitizing Agents; C491805:Ube1c protein, mouse; D014452:Ubiquitins; C101467:XRCC4 protein, human; C511788:XRCC4 protein, mouse; D025821:Polyubiquitin; D044767:Ubiquitin-Protein Ligases; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; C497264:Prkdc protein, mouse; D044764:Ubiquitin-Activating Enzymes; C491802:NAE protein, human; D008239:Lysine; C539933:pevonedistat