p53-dependent cell cycle arrests are preserved in DNA-activated protein kinase-deficient mouse fibroblasts

Cancer Res. 1996 Jul 1;56(13):2940-4.


p53 is involved in at least three cell cycle checkpoints in normal cells: two in G1, activated by either DNA damage or by ribonucleotide pool depletion in the absence of damage, and one in metaphase/anaphase activated by an incomplete mitotic spindle. We tested whether any of these checkpoints require the DNA-activated protein kinase (DNAPK), since data indicate that it is activated by damaged DNA to modify p53 in cultured cells and in cell-free systems. Fibroblasts isolated from mice with severe combined immune deficiency (SCID) were used because the sole genetic defect underlying this syndrome lies within the DNAPK gene. This report shows that age-matched SCID and isogenic wild-type embryonic fibroblasts arrested in response to DNA damage, ribonucleoside triphosphate depletion, and spindle poisons, whereas p53-/- fibroblasts failed to do so. Therefore, DNAPK-deficient scid cells preserve normal p53-dependent cell cycle checkpoints. The data provide one explanation of why scid mice are not tumor prone though they are deficient in double-strand break repair.

Publication types

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

MeSH terms

  • Animals
  • Antimetabolites, Antineoplastic / pharmacology
  • Aspartic Acid / analogs & derivatives
  • Aspartic Acid / pharmacology
  • Base Sequence
  • Cell Cycle / physiology
  • Cells, Cultured
  • DNA Damage
  • DNA-Activated Protein Kinase
  • DNA-Binding Proteins*
  • Embryo, Mammalian
  • Female
  • Fibroblasts / cytology
  • Fibroblasts / enzymology
  • Fibroblasts / physiology*
  • G1 Phase / physiology
  • Male
  • Mice
  • Mice, Knockout
  • Mice, SCID
  • Micronuclei, Chromosome-Defective / genetics
  • Molecular Sequence Data
  • Phosphonoacetic Acid / analogs & derivatives
  • Phosphonoacetic Acid / pharmacology
  • Protein Serine-Threonine Kinases / deficiency*
  • Ribonucleotides / metabolism
  • Spindle Apparatus / physiology
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / physiology*


  • Antimetabolites, Antineoplastic
  • DNA-Binding Proteins
  • Ribonucleotides
  • Tumor Suppressor Protein p53
  • Aspartic Acid
  • sparfosic acid
  • DNA-Activated Protein Kinase
  • Protein Serine-Threonine Kinases
  • Phosphonoacetic Acid