title: Cell polarity protein Par3 complexes with DNA-PK via Ku70 and regulates DNA double-strand break repair.
abstract: The partitioning-defective 3 (Par3), a key component in the conserved Par3/Par6/aPKC complex, plays fundamental roles in cell polarity. Herein we report the identification of Ku70 and Ku80 as novel Par3-interacting proteins through an in vitro binding assay followed by liquid chromatography-tandem mass spectrometry. Ku70/Ku80 proteins are two key regulatory subunits of the DNA-dependent protein kinase (DNA-PK), which plays an essential role in repairing double-strand DNA breaks (DSBs). We determined that the nuclear association of Par3 with Ku70/Ku80 was enhanced by gamma-irradiation (IR), a potent DSB inducer. Furthermore, DNA-PKcs, the catalytic subunit of DNA-PK, interacted with the Par3/Ku70/Ku80 complex in response to IR. Par3 over-expression or knockdown was capable of up- or downregulating DNA-PK activity, respectively. Moreover, the Par3 knockdown cells were found to be defective in random plasmid integration, defective in DSB repair following IR, and radiosensitive, phenotypes similar to that of Ku70 knockdown cells. These findings identify Par3 as a novel component of the DNA-PK complex and implicate an unexpected link of cell polarity to DSB repair.
authors.affiliation: Key Laboratory of Proteomics and Laboratory of Molecular Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Longhou
authors.initials: L
authors.lastname: Fang
authors.forename: YiGuo
authors.initials: Y
authors.lastname: Wang
authors.forename: Dan
authors.initials: D
authors.lastname: Du
authors.forename: Guang
authors.initials: G
authors.lastname: Yang
authors.forename: Tim
authors.initials: T
authors.lastname: Tak Kwok
authors.forename: Siu
authors.initials: S
authors.lastname: Kai Kong
authors.forename: Benjamin
authors.initials: B
authors.lastname: Chen
authors.forename: David J
authors.initials: DJ
authors.lastname: Chen
authors.forename: Zhengjun
authors.initials: Z
authors.lastname: Chen
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D034961:Antigens, Nuclear / Q000502:physiology*; D018938:Caco-2 Cells; D020134:Catalytic Domain / Q000502:physiology; D018797:Cell Cycle Proteins / Q000502:physiology*; D016764:Cell Polarity / Q000502:physiology*; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000502:physiology*; D051747:DNA-Activated Protein Kinase / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D000072200:Ku Autoantigen; D008565:Membrane Proteins / Q000502:physiology*; D009687:Nuclear Proteins / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D034961:Antigens, Nuclear; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; C509689:PARD3 protein, human; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen