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The DNA-dependent protein kinase: requirement for DNA ends and association with Ku antigen.

The DNA-dependent protein kinase (DNA-PK) phosphorylates Sp1 and several other nuclear proteins. Here, we show that Sp1 and the DNA-PK must be colocalized on the same DNA molecule for efficient phosphorylation to occur. Interestingly, we find that the DNA-PK binds to and is activated by the ends of DNA molecules. Furthermore, we show that the DNA binding properties of the DNA-PK are identical to those of Ku, a well-characterized human autoimmune antigen. We demonstrate that the DNA-PK can be fractionated into two components, one of which is Ku and the other of which is a polypeptide of approximately 350 kd. DNA cross-linking and coimmunoprecipitation studies indicate that the catalytic 350 kd DNA-PK component is directed to DNA by protein-protein interactions with Ku. The implications of the unusual DNA binding mode and multicomponent nature of the DNA-PK are discussed.

Pubmed ID: 8422676


  • Gottlieb TM
  • Jackson SP



Publication Data

January 15, 1993

Associated Grants

  • Agency: Wellcome Trust, Id:

Mesh Terms

  • Antigens, Nuclear
  • Base Sequence
  • DNA
  • DNA Helicases
  • DNA, Single-Stranded
  • DNA-Binding Proteins
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Nuclear Proteins
  • Phosphorylation
  • Precipitin Tests
  • Protein Binding
  • Protein Kinases
  • Sp1 Transcription Factor