DNA damage mediated s and g(2) checkpoints in human embryonal carcinoma cells

Stem Cells. 2009 Mar;27(3):568-76. doi: 10.1634/stemcells.2008-0690.

Abstract

For mouse embryonic stem (ES) cells, the importance of the S and G(2) cell cycle checkpoints for genomic integrity is increased by the absence of the G(1) checkpoint. We have investigated ionizing radiation (IR)-mediated cell cycle checkpoints in undifferentiated and retinoic acid-differentiated human embryonal carcinoma (EC) cells. Like mouse ES cells, human EC cells did not undergo G(1) arrest after IR but displayed a prominent S-phase delay followed by a G(2)-phase delay. In contrast, although differentiated EC cells also failed to arrest at G(1)-phase after IR, they quickly exited S-phase and arrested in G(2)-phase. In differentiated EC cells, the G(2)-M-phase cyclin B1/CDC2 complex was upregulated after IR, but the G(1)-S-phase cyclin E and the cyclin E/CDK2 complex were expressed at constitutively low levels, which could be an important factor distinguishing DNA damage responses between undifferentiated and differentiated EC cells. S-phase arrest and expression of p21 could be inhibited by 7-hydroxystaurosporine, suggesting that the ataxia-telangiectasia and Rad-3-related-checkpoint kinase 1 (ATR-CHK1), and p21 pathways might play a role in the IR-mediated S-phase checkpoint in EC cells. IR-mediated phosphorylation of ataxia-telangiectasia mutated, (CHK1), and checkpoint kinase 2 were distinctly higher in undifferentiated EC cells compared with differentiated EC cells. Combined with the prominent S and G(2) checkpoints and a more efficient DNA damage repair system, these mechanisms operate together in the maintenance of genome stability for EC cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Cell Line
  • Cell Survival / genetics
  • Cell Survival / physiology
  • Checkpoint Kinase 2
  • Cyclin E / metabolism
  • DNA Damage / genetics*
  • DNA Damage / physiology
  • Embryonal Carcinoma Stem Cells / cytology*
  • Embryonal Carcinoma Stem Cells / metabolism*
  • G2 Phase / genetics*
  • Humans
  • Immunoprecipitation
  • Protein Serine-Threonine Kinases / metabolism
  • S Phase / genetics*

Substances

  • Cyclin E
  • Checkpoint Kinase 2
  • CHEK2 protein, human
  • Chek2 protein, mouse
  • Protein Serine-Threonine Kinases