Chronic hypoxia compromises repair of DNA double-strand breaks to drive genetic instability

Ramya Kumareswaran, Olga Ludkovski, Alice Meng, Jenna Sykes, Melania Pintilie, Robert G. Bristow

Research output: Contribution to journalArticlepeer-review

Abstract

Hypoxic cells have been linked to genetic instability and tumor progression. However, little is known about the exact relationship between DNA repair and genetic instability in hypoxic cells. We therefore tested whether the sensing and repair of DNA double-strand breaks (DNA-dsbs) is altered in irradiated cells kept under continual oxic, hypoxic or anoxic conditions. Synchronized G0-G1 human fibroblasts were irradiated (0-10 Gy) after initial gassing with 0% O2 (anoxia), 0.2% O2 (hypoxia) or 21% O2 (oxia) for 16 hours. The response of phosphorylated histone H2AX (γ-H2AX), phosphorylated ataxia telangiectasia mutated [ATM(Ser1981)], and the p53 binding protein 1 (53BP1) was quantified by intranuclear DNA repair foci and western blotting. At 24 hours following DNA damage, residual γ-H2AX, ATM(Ser1981) and 53BP1 foci were observed in hypoxic cells. This increase in residual DNA-dsbs under hypoxic conditions was confirmed using neutral comet assays. Clonogenic survival was also reduced in chronically hypoxic cells, which is consistent with the observation of elevated G1-associated residual DNA-dsbs. We also observed an increase in the frequency of chromosomal aberrations in chronically hypoxic cells. We conclude that DNA repair under continued hypoxia leads to decreased repair of G1-associated DNA-dsbs, resulting in increased chromosomal instability. Our findings suggest that aberrant DNA-dsb repair under hypoxia is a potential factor in hypoxia-mediated genetic instability.

Original languageEnglish
Pages (from-to)189-199
Number of pages11
JournalJournal of Cell Science
Volume125
Issue number1
DOIs
Publication statusPublished - 1 Jan 2012

Keywords

  • γ-H2AX
  • DNA double-strand break sensors
  • DNA double-strand breaks
  • Genetic instability
  • Hypoxia
  • Non-homologous end joining

Research Beacons, Institutes and Platforms

  • Manchester Cancer Research Centre

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