title: MDC1 regulates DNA-PK autophosphorylation in response to DNA damage.
abstract: DNA damage initiates signaling events through kinase cascades that result in cell cycle checkpoint control and DNA repair. However, it is not yet clear how the signaling pathways relay to DNA damage repair. Using the repeat region of checkpoint protein MDC1 (mediator of DNA damage checkpoint protein 1), we identified DNA-PKcs/Ku as MDC1-associated proteins. Here, we show that MDC1 directly interacts with the Ku/DNA-PKcs complex. Down-regulation of MDC1 resulted in defective phospho-DNA-PKcs foci formation and DNA-PKcs autophosphorylation, suggesting that MDC1 regulates autophosphorylation of DNA-PKcs following DNA damage. Furthermore, DNA-PK-dependent DNA damage repair is defective in cells depleted of MDC1. Taken together, these results suggest that the MDC1 repeat region is involved in protein-protein interaction with DNA-PKcs/Ku, and MDC1 regulates DNA damage repair by influencing DNA-PK autophosphorylation. Therefore, MDC1 acts not only as a mediator of DNA damage checkpoint but also as a mediator of DNA damage repair.
authors.affiliation: Department of Oncology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
authors.forename: Zhenkun
authors.initials: Z
authors.lastname: Lou
authors.forename: Benjamin Ping-Chi
authors.initials: BP
authors.lastname: Chen
authors.forename: Aroumougame
authors.initials: A
authors.lastname: Asaithamby
authors.forename: Katherine
authors.initials: K
authors.lastname: Minter-Dykhouse
authors.forename: David J
authors.initials: DJ
authors.lastname: Chen
authors.forename: Junjie
authors.initials: J
authors.lastname: Chen
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology*; D015536:Down-Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins / Q000502:physiology*; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D015534:Trans-Activators / Q000502:physiology*; D014162:Transfection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C413163:MDC1 protein, human; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D015534:Trans-Activators; D004247:DNA; D005982:Glutathione Transferase; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases