Heat Sensitivity of Double-Stranded DNA-dependent Protein Kinase (DNA-PK) Activity

Int J Radiat Biol. 1999 Feb;75(2):253-8. doi: 10.1080/095530099140717.


Purpose: The heat sensitivity of DNA-PK activity in hybrid cells and the possible restoration of this activity with extracts from scid cells (defective in DNA-PKcs), sxi-3 cells (defective in Ku80) and V794 (sxi-3 parental wild-type cells) was analysed.

Materials and methods: Heat treatment of cells was performed in a water bath at 44 degrees C. The cell extract from scid cells or sxi-3 cells was added to heat-treated hybrid cell extracts, and the DNA-PK activity was assayed.

Results: When hybrid cells were heated at 44 degrees C for 15 min, DNA-PK activity was reduced to undetectable levels. The decreased DNA-PK activity could be restored in a concentration-dependent manner with the addition of scid cell extract. The sxi-3 cell extract could not restore heat-inactivated DNA-PK activity.

Conclusions: DNA-PK was inactivated by heat treatment at 44 degrees C. Ku70/Ku80, but not Ku70 alone, could restore heat-inactivated DNA-PK.

MeSH terms

  • Animals
  • Antigens, Nuclear*
  • Cell Extracts / immunology
  • Cell Extracts / pharmacology
  • Cricetinae
  • DNA Helicases*
  • DNA Repair
  • DNA-Activated Protein Kinase
  • DNA-Binding Proteins / immunology
  • Enzyme Activation / drug effects
  • Fibroblasts / enzymology
  • Hot Temperature*
  • Humans
  • Hybrid Cells
  • Immune Sera / pharmacology
  • Ku Autoantigen
  • Mice
  • Mice, SCID
  • Nuclear Proteins / immunology
  • Protein-Serine-Threonine Kinases / immunology
  • Protein-Serine-Threonine Kinases / metabolism*


  • Antigens, Nuclear
  • Cell Extracts
  • DNA-Binding Proteins
  • Immune Sera
  • Nuclear Proteins
  • DNA-Activated Protein Kinase
  • PRKDC protein, human
  • Protein-Serine-Threonine Kinases
  • DNA Helicases
  • XRCC5 protein, human
  • Xrcc6 protein, human
  • Xrcc6 protein, mouse
  • Ku Autoantigen