DNA damage checkpoint kinase Chk2 triggers replicative senescence

EMBO J. 2004 Jul 7;23(13):2554-63. doi: 10.1038/sj.emboj.7600259. Epub 2004 Jun 10.


Telomere shortening in normal human cells causes replicative senescence, a p53-dependent growth arrest state, which is thought to represent an innate defence against tumour progression. However, although it has been postulated that critical telomere loss generates a 'DNA damage' signal, the signalling pathway(s) that alerts cells to short dysfunctional telomeres remains only partially defined. We show that senescence in human fibroblasts is associated with focal accumulation of gamma-H2AX and phosphorylation of Chk2, known mediators of the ataxia-telangiectasia mutated regulated signalling pathway activated by DNA double-strand breaks. Both these responses increased in cells grown beyond senescence through inactivation of p53 and pRb, indicating that they are driven by continued cell division and not a consequence of senescence. gamma-H2AX (though not Chk2) was shown to associate directly with telomeric DNA. Furthermore, inactivation of Chk2 in human fibroblasts led to a fall in p21(waf1) expression and an extension of proliferative lifespan, consistent with failure to activate p53. Thus, Chk2 forms an essential component of a common pathway signalling cell cycle arrest in response to both telomere erosion and DNA damage.

Publication types

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

MeSH terms

  • Blotting, Western
  • Cell Cycle Proteins / metabolism
  • Cell Cycle*
  • Cell Line
  • Cell Proliferation
  • Cellular Senescence*
  • Checkpoint Kinase 2
  • Chromatin Immunoprecipitation
  • Cyclin-Dependent Kinase Inhibitor p21
  • DNA / metabolism*
  • DNA Damage*
  • DNA Replication*
  • Fibroblasts / metabolism
  • Fluorescent Antibody Technique, Indirect
  • Fluorescent Dyes
  • Genes, Tumor Suppressor
  • Histones / metabolism
  • Humans
  • Lung / cytology
  • Male
  • Microscopy, Confocal
  • Models, Biological
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA, Small Interfering / metabolism
  • Retinoblastoma Protein / metabolism
  • Retroviridae / genetics
  • Telomerase / metabolism
  • Telomere / metabolism
  • Tumor Suppressor Protein p53 / metabolism
  • Xanthenes


  • CDKN1A protein, human
  • Cell Cycle Proteins
  • Cyclin-Dependent Kinase Inhibitor p21
  • Fluorescent Dyes
  • H2AX protein, human
  • Histones
  • RNA, Small Interfering
  • Retinoblastoma Protein
  • Tumor Suppressor Protein p53
  • Xanthenes
  • Texas red
  • DNA
  • Checkpoint Kinase 2
  • CHEK2 protein, human
  • Protein-Serine-Threonine Kinases
  • Telomerase