A positive role for the Ku complex in DNA replication following strand break damage in mammals

J Biol Chem. 2004 Feb 13;279(7):6046-55. doi: 10.1074/jbc.M311054200. Epub 2003 Nov 15.


Ku70-Ku80 complex is the regulatory subunit of DNA-dependent protein kinase (DNA-PK) and plays an essential role in double-strand break repair following ionizing radiation (IR). It preferentially interacts with chromosomal breaks and protects DNA ends from nuclease attack. Here we show evidence that cells defective in Ku80 exhibit a significantly slow S phase progression following DNA damage. IR-induced retardation in S phase progression in Ku80-/- cells was not due to the lack of DNA-PK kinase activity because both wild-type cells and DNA-PKcs-deficient cells showed no such symptom. Instead, proliferating cell nuclear antigen (PCNA) dissociated from chromosomes following IR in Ku80-deficient cells but not in wild-type or DNA-PKcs-deficient cells. Treatment of HeLa cells with IR induced colocalization of the Ku complex with PCNA on chromosomes. Together, these results suggest that binding of the Ku complex at chromosomal breaks may be necessary to maintain the sliding clamps (PCNA) on chromatin, which would allow cells to resume DNA replication without a major delay following IR.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antigens, Nuclear / biosynthesis
  • Antigens, Nuclear / physiology*
  • Bromodeoxyuridine / pharmacology
  • Cell Cycle
  • Cell Nucleus / metabolism
  • Chromatin / chemistry
  • Chromatin / metabolism
  • Cytosol / metabolism
  • DNA Damage
  • DNA Helicases*
  • DNA Repair
  • DNA Replication*
  • DNA-Binding Proteins / biosynthesis
  • DNA-Binding Proteins / physiology*
  • Dimerization
  • Dose-Response Relationship, Radiation
  • HeLa Cells
  • Humans
  • Ku Autoantigen
  • Mice
  • Microscopy, Confocal
  • Proliferating Cell Nuclear Antigen / chemistry
  • Proliferating Cell Nuclear Antigen / metabolism
  • Protein Binding
  • Radiation, Ionizing
  • Time Factors


  • Antigens, Nuclear
  • Chromatin
  • DNA-Binding Proteins
  • Proliferating Cell Nuclear Antigen
  • DNA Helicases
  • XRCC5 protein, human
  • Xrcc6 protein, human
  • Xrcc6 protein, mouse
  • Ku Autoantigen
  • Bromodeoxyuridine