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Isolation of Ku70-binding proteins (KUBs).

DNA-dependent protein kinase (DNA-PK) plays a critical role in resealing DNA double-stand breaks by non-homologous end joining. Aside from DNA-PK, XRCC4 and DNA ligase IV, other proteins which play a role(s) in this repair pathway remain unknown; DNA-PK contains a catalytic subunit (DNA-PKcs) and a DNA binding subunit (Ku70 and Ku80). We isolated Ku70-binding proteins (KUB1-KUB4) using yeast two-hybrid analyses. Sequence analyses revealed KUB1 to be apolipoprotein J (apoJ), also known as X-ray-inducible transcript 8 (XIP8), testosterone-repressed prostate message-2 (TRPM-2) and clusterin. KUB2 is Ku80. KUB3 and KUB4 are unknown, >10 kb trans-cripts. Interactions of apoJ/XIP8 or KUB3 with Ku70 were confirmed by co-immunoprecipitation analyses in MCF-7:WS8 breast cancer or IMR-90 normal lung fibroblast cells, respectively. The interaction of apoJ/XIP8 with Ku70 was confirmed by far-western analyses. Stable over-expression of full-length apoJ/XIP8 in MCF-7:WS8 caused decreased Ku70/Ku80 DNA end binding that was restored by apoJ/XIP8 monoclonal antibodies. The role of apoJ/XIP8 in ionizing radiation resistance/sensitivity is under investigation.

Pubmed ID: 10219089


  • Yang CR
  • Yeh S
  • Leskov K
  • Odegaard E
  • Hsu HL
  • Chang C
  • Kinsella TJ
  • Chen DJ
  • Boothman DA


Nucleic acids research

Publication Data

May 15, 1999

Associated Grants

  • Agency: NCI NIH HHS, Id: CA-50595
  • Agency: NCI NIH HHS, Id: CA-ES78530
  • Agency: NCI NIH HHS, Id: CA50519
  • Agency: NCI NIH HHS, Id: R01 CA139217

Mesh Terms

  • Animals
  • Antigens, Nuclear
  • Base Sequence
  • Carrier Proteins
  • Cell Line
  • Cloning, Molecular
  • Clusterin
  • DNA Helicases
  • DNA Probes
  • DNA Repair
  • DNA-Activated Protein Kinase
  • DNA-Binding Proteins
  • Glycoproteins
  • Humans
  • Mice
  • Molecular Chaperones
  • Nuclear Proteins
  • Protein Binding
  • Protein-Serine-Threonine Kinases
  • Recombinant Proteins
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Tumor Cells, Cultured