title: Cell cycle dependence of DNA-dependent protein kinase phosphorylation in response to DNA double strand breaks.
abstract: DNA-dependent protein kinase (DNA-PK), consisting of Ku and DNA-PKcs subunits, is the key component of the non-homologous end-joining (NHEJ) pathway of DNA double strand break (DSB) repair. Although the kinase activity of DNA-PKcs is essential for NHEJ, thus far, no in vivo substrate has been conclusively identified except for an autophosphorylation site on DNA-PKcs itself (threonine 2609). Here we report the ionizing radiation (IR)-induced autophosphorylation of DNA-PKcs at a novel site, serine 2056, the phosphorylation of which is required for the repair of DSBs by NHEJ. Interestingly, IR-induced DNA-PKcs autophosphorylation is regulated in a cell cycle-dependent manner with attenuated phosphorylation in the S phase. In contrast, DNA replication-associated DSBs resulted in DNA-PKcs autophosphorylation and localization to DNA damage sites. These results indicate that although IR-induced DNA-PKcs phosphorylation is attenuated in the S phase, DNA-PKcs is preferentially activated by the physiologically relevant DNA replication-associated DSBs at the sites of DNA synthesis.
authors.affiliation: Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9187, USA. benjamin.chen@utsouthwestern.edu <benjamin.chen@utsouthwestern.edu>
authors.forename: Benjamin P C
authors.initials: BP
authors.lastname: Chen
authors.forename: Doug W
authors.initials: DW
authors.lastname: Chan
authors.forename: Junya
authors.initials: J
authors.lastname: Kobayashi
authors.forename: Sandeep
authors.initials: S
authors.lastname: Burma
authors.forename: Aroumougame
authors.initials: A
authors.lastname: Asaithamby
authors.forename: Keiko
authors.initials: K
authors.lastname: Morotomi-Yano
authors.forename: Elliot
authors.initials: E
authors.lastname: Botvinick
authors.forename: Jun
authors.initials: J
authors.lastname: Qin
authors.forename: David J
authors.initials: DJ
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D002453:Cell Cycle; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005822:Genetic Vectors; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D011839:Radiation, Ionizing; D016196:S Phase; D012694:Serine / Q000737:chemistry; D013912:Threonine / Q000737:chemistry
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D013912:Threonine; D012694:Serine; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases