Letter | Published:

Counting RAD51 proteins disassembling from nucleoprotein filaments under tension

Nature volume 457, pages 745748 (05 February 2009) | Download Citation


The central catalyst in eukaryotic ATP-dependent homologous recombination consists of RAD51 proteins, polymerized around single-stranded DNA. This nucleoprotein filament recognizes and invades a homologous duplex DNA segment1,2. After strand exchange, the nucleoprotein filament should disassemble so that the recombination process can be completed3. The molecular mechanism of RAD51 filament disassembly is poorly understood. Here we show, by combining optical tweezers with single-molecule fluorescence microscopy and microfluidics4,5, that disassembly of human RAD51 nucleoprotein filaments results from the interplay between ATP hydrolysis and the release of the tension stored in the filament. By applying external tension to the DNA, we found that disassembly slows down and can even be stalled. We quantified the fluorescence of RAD51 patches and found that disassembly occurs in bursts interspersed by long pauses. After relaxation of a stalled complex, pauses were suppressed resulting in a large burst. These results indicate that tension-dependent disassembly takes place only from filament ends, after tension-independent ATP hydrolysis. This integrative single-molecule approach allowed us to dissect the mechanism of this principal homologous recombination reaction step, which in turn clarifies how disassembly can be influenced by accessory proteins.

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We thank B. van den Broek and R.T. Dame for discussions and a critical reading of the manuscript and J. Kerssemakers for kindly providing his step fitting algorithm. This work was supported by the Biomolecular Physics program of the Dutch organization for Fundamental Research of Matter (FOM) (to R.K., C.W., E.J.G.P. and G.J.L.W.), and grants from the Dutch Cancer Society (KWF), the Netherlands Organization for Scientific Research (NWO), the Netherlands Genomics Initiative/NWO, the Association for International Cancer Research and the European Commission Integrated Projects Molecular Imaging and DNA Repair and a National Cancer Institute–National Institutes of Health USA program project (to C.W. and R.K.). E.J.G.P. and G.J.L.W. are recipients of NWO Vidi grants; C.W. of an NWO Vici grant.

Author information

Author notes

    • Joost van Mameren

    Present address: JPK Instruments AG, Bouchéstrasse 12, 12435 Berlin, Germany.

    • Erwin J. G. Peterman
    •  & Gijs J. L. Wuite

    These authors contributed equally to this work.


  1. Laser Centre and Department of Physics and Astronomy, VU University, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands

    • Joost van Mameren
    • , Erwin J. G. Peterman
    •  & Gijs J. L. Wuite
  2. Department of Cell Biology and Genetics, Erasmus MC, PO Box 2040, 3000 CA Rotterdam, The Netherlands

    • Mauro Modesti
    • , Roland Kanaar
    •  & Claire Wyman
  3. CNRS, Unité Propre de Recherche 3081, Genome Instability and Carcinogenesis Conventionné par l'Université d'Aix-Marseille 2, 13402 Marseille Cedex 20, France

    • Mauro Modesti
  4. Department of Radiation Oncology, Erasmus MC, PO Box 2040, 3000 CA Rotterdam, The Netherlands

    • Roland Kanaar
    •  & Claire Wyman


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Corresponding authors

Correspondence to Erwin J. G. Peterman or Gijs J. L. Wuite.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    This file contains Supplementary Methods, Supplementary Figures S1-S6 with Legends and Supplementary References


  1. 1.

    Supplementary Video 1

    Supplementary Video 1 on which the data in Figure 1b is based, shows an individual RAD51–DNA complex, suspended in a buffer flow from a single optically trapped bead. At about one third of the video, the complex is moved to a Mg2+-containing buffer channel, triggering disassembly as evidenced by the concurrent intensity decrease and shrinkage of the entire complex. The video is sped up 200 ×.

  2. 2.

    Supplementary Video 2

    Supplementary Video 2 on which the data in Figure 2a is based, shows that RAD51 filament disassembly is slowed down by tension applied to the DNA. The video displays a graph of the decreasing fluorescence intensity (white) and the increasing tension (red) signals. The video is sped up 300 ×.

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