Molecular flexibility of DNA as a key determinant of RAD51 recruitment

EMBO J. 2020 Apr 1;39(7):e103002. doi: 10.15252/embj.2019103002. Epub 2020 Jan 14.


The timely activation of homologous recombination is essential for the maintenance of genome stability, in which the RAD51 recombinase plays a central role. Biochemically, human RAD51 polymerises faster on single-stranded DNA (ssDNA) compared to double-stranded DNA (dsDNA), raising a key conceptual question: how does it discriminate between them? In this study, we tackled this problem by systematically assessing RAD51 binding kinetics on ssDNA and dsDNA differing in length and flexibility using surface plasmon resonance. By directly fitting a mechanistic model to our experimental data, we demonstrate that the RAD51 polymerisation rate positively correlates with the flexibility of DNA. Once the RAD51-DNA complex is formed, however, RAD51 remains stably bound independent of DNA flexibility, but rapidly dissociates from flexible DNA when RAD51 self-association is perturbed. This model presents a new general framework suggesting that the flexibility of DNA, which may increase locally as a result of DNA damage, plays an important role in rapidly recruiting repair factors that multimerise at sites of DNA damage.

Keywords: RAD51; double-stranded DNA; mathematical model; single-stranded DNA; surface plasmon resonance.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • DNA / chemistry*
  • DNA / metabolism*
  • DNA Repair
  • Humans
  • Models, Theoretical
  • Point Mutation
  • Protein Binding
  • Rad51 Recombinase / chemistry*
  • Rad51 Recombinase / genetics
  • Rad51 Recombinase / metabolism*
  • Scattering, Small Angle
  • Surface Plasmon Resonance
  • X-Ray Diffraction


  • DNA
  • RAD51 protein, human
  • Rad51 Recombinase