ATM alters the otherwise robust chromatin mobility at sites of DNA double-strand breaks (DSBs) in human cells

PLoS One. 2014 Mar 20;9(3):e92640. doi: 10.1371/journal.pone.0092640. eCollection 2014.

Abstract

Ionizing radiation induces DNA double strand breaks (DSBs) which can lead to the formation of chromosome rearrangements through error prone repair. In mammalian cells the positional stability of chromatin contributes to the maintenance of genome integrity. DSBs exhibit only a small, submicron scale diffusive mobility, but a slight increase in the mobility of chromatin domains by the induction of DSBs might influence repair fidelity and the formation of translocations. The radiation-induced local DNA decondensation in the vicinity of DSBs is one factor potentially enhancing the mobility of DSB-containing chromatin domains. Therefore in this study we focus on the influence of different chromatin modifying proteins, known to be activated by the DNA damage response, on the mobility of DSBs. IRIF (ionizing radiation induced foci) in U2OS cells stably expressing 53BP1-GFP were used as a surrogate marker of DSBs. Low angle charged particle irradiation, known to trigger a pronounced DNA decondensation, was used for the defined induction of linear tracks of IRIF. Our results show that movement of IRIF is independent of the investigated chromatin modifying proteins like ACF1 or PARP1 and PARG. Also depletion of proteins that tether DNA strands like MRE11 and cohesin did not alter IRIF dynamics significantly. Inhibition of ATM, a key component of DNA damage response signaling, resulted in a pronounced confinement of DSB mobility, which might be attributed to a diminished radiation induced decondensation. This confinement following ATM inhibition was confirmed using X-rays, proving that this effect is not restricted to densely ionizing radiation. In conclusion, repair sites of DSBs exhibit a limited mobility on a small spatial scale that is mainly unaffected by depletion of single remodeling or DNA tethering proteins. However, it relies on functional ATM kinase which is considered to influence the chromatin structure after irradiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ataxia Telangiectasia Mutated Proteins / genetics
  • Ataxia Telangiectasia Mutated Proteins / metabolism*
  • Cell Cycle Proteins / metabolism
  • Cell Line
  • Chromatin / genetics*
  • Chromatin / metabolism*
  • Chromatin Assembly and Disassembly
  • Chromosomal Proteins, Non-Histone / metabolism
  • Cohesins
  • DNA Breaks, Double-Stranded*
  • DNA Repair
  • Gene Expression
  • Gene Knockdown Techniques
  • Genes, Reporter
  • Humans
  • Multiprotein Complexes / metabolism
  • Poly(ADP-ribose) Polymerases / metabolism
  • Transcription Factors / metabolism

Substances

  • BAZ1A protein, human
  • Cell Cycle Proteins
  • Chromatin
  • Chromosomal Proteins, Non-Histone
  • Multiprotein Complexes
  • Transcription Factors
  • Poly(ADP-ribose) Polymerases
  • Ataxia Telangiectasia Mutated Proteins

Grants and funding

This work was supported by DFG funded GRK 1657 and the Helmholtz graduate school for hadron and ion research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.