A Mechanism to Minimize Errors during Non-homologous End Joining

Mol Cell. 2020 Mar 5;77(5):1080-1091.e8. doi: 10.1016/j.molcel.2019.11.018. Epub 2019 Dec 17.


Enzymatic processing of DNA underlies all DNA repair, yet inappropriate DNA processing must be avoided. In vertebrates, double-strand breaks are repaired predominantly by non-homologous end joining (NHEJ), which directly ligates DNA ends. NHEJ has the potential to be highly mutagenic because it uses DNA polymerases, nucleases, and other enzymes that modify incompatible DNA ends to allow their ligation. Using frog egg extracts that recapitulate NHEJ, we show that end processing requires the formation of a "short-range synaptic complex" in which DNA ends are closely aligned in a ligation-competent state. Furthermore, single-molecule imaging directly demonstrates that processing occurs within the short-range complex. This confinement of end processing to a ligation-competent complex ensures that DNA ends undergo ligation as soon as they become compatible, thereby minimizing mutagenesis. Our results illustrate how the coordination of enzymatic catalysis with higher-order structural organization of substrate maximizes the fidelity of DNA repair.

Keywords: NHEJ; end processing; non-homologous end joining; single-molecule; smFRET.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • DNA Breaks, Double-Stranded*
  • DNA End-Joining Repair*
  • DNA Ligases / genetics
  • DNA Ligases / metabolism
  • DNA Repair Enzymes / genetics
  • DNA Repair Enzymes / metabolism
  • DNA-Activated Protein Kinase / genetics
  • DNA-Activated Protein Kinase / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Female
  • Genomic Instability*
  • Ku Autoantigen / genetics
  • Ku Autoantigen / metabolism
  • Models, Genetic
  • Multiprotein Complexes
  • Phosphoric Diester Hydrolases / genetics
  • Phosphoric Diester Hydrolases / metabolism
  • Single Molecule Imaging
  • Time Factors
  • Xenopus Proteins / genetics
  • Xenopus Proteins / metabolism
  • Xenopus laevis


  • DNA-Binding Proteins
  • Multiprotein Complexes
  • Xenopus Proteins
  • DNA-Activated Protein Kinase
  • Phosphoric Diester Hydrolases
  • Ku Autoantigen
  • DNA Ligases
  • DNA Repair Enzymes