Differing Responses of Nijmegen Breakage Syndrome and Ataxia Telangiectasia Cells to Ionizing Radiation

Radiat Res. 2002 Sep;158(3):319-26. doi: 10.1667/0033-7587(2002)158[0319:dronbs]2.0.co;2.


Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder. Originally thought to be a variant of ataxia telangiectasia (AT), the cellular phenotype of NBS has been described as almost indistinguishable from that of AT. Since the gene involved in NBS has been cloned and its functions studied, we sought to further characterize its cellular phenotype by examining the response of density-inhibited, confluent cultures of human diploid fibroblasts to irradiation in the G(0)/G(1) phase of the cell cycle. Both NBS and AT cells were markedly sensitive to the cytotoxic effects of radiation. NBS cells, however, were proficient in recovery from potentially lethal damage and exhibited a pronounced radiation-induced G(1)-phase arrest. Irradiated AT cells showed no potentially lethal damage and no G(1)-phase arrest. Both cell types were hypersensitive to the induction of chromosomal aberrations, whereas the distribution of aberrations in irradiated NBS cells was similar to that of normal controls, AT cells showed a high frequency of chromatid-type aberrations. TP53 and CDKN1A (also known as p21(Waf1)) expression was attenuated in irradiated NBS cells, but maximal induction occurred 2 h postirradiation, as was observed in normal controls. The similarities and differences in cellular phenotype between irradiated NBS and AT cells are discussed in terms of the functional properties of the signaling pathways downstream of AT involving the NBS1 and TP53 proteins.

Publication types

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

MeSH terms

  • Abnormalities, Multiple / genetics
  • Abnormalities, Multiple / pathology
  • Ataxia Telangiectasia / pathology*
  • Ataxia Telangiectasia Mutated Proteins
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / physiology
  • Cells, Cultured / radiation effects
  • Chromatids / radiation effects
  • Chromosome Breakage*
  • Chromosome Fragility*
  • Chromosomes, Human / radiation effects*
  • DNA Damage
  • DNA Repair
  • DNA-Binding Proteins
  • Fibroblasts / chemistry
  • Fibroblasts / radiation effects
  • G1 Phase / radiation effects
  • Humans
  • Immunologic Deficiency Syndromes / genetics
  • Immunologic Deficiency Syndromes / pathology
  • Neoplastic Syndromes, Hereditary / pathology*
  • Nuclear Proteins / deficiency
  • Nuclear Proteins / genetics
  • Nuclear Proteins / physiology
  • Protein-Serine-Threonine Kinases / deficiency
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / physiology
  • Resting Phase, Cell Cycle / radiation effects
  • Signal Transduction
  • Syndrome
  • Tumor Suppressor Protein p53 / physiology
  • Tumor Suppressor Proteins


  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • NBN protein, human
  • Nuclear Proteins
  • Tumor Suppressor Protein p53
  • Tumor Suppressor Proteins
  • ATM protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • Protein-Serine-Threonine Kinases