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Nature 418, 562-566 (1 August 2002) | doi:10.1038/nature00922; Received 18 April 2002; Accepted 28 May 2002; Corrected 12 August 2002

The Rad50 zinc-hook is a structure joining Mre11 complexes in DNA recombination and repair

Karl-Peter Hopfner2,8, Lisa Craig1,8, Gabriel Moncalian1, Robert A. Zinkel3, Takehiko Usui4, Barbara A. L. Owen5, Annette Karcher2, Brendan Henderson6, Jean-Luc Bodmer1, Cynthia T. McMurray5, James P. Carney6, John H. J. Petrini4 & John A. Tainer1,7

  1. Department of Molecular Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA
  2. Gene Center and Institute of Biochemistry, University of Munich, 81377 Munich, Germany
  3. Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53706, USA
  4. Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA
  5. Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
  6. The Radiation Oncology Research Laboratory, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
  7. Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
  8. These authors contributed equally to this work.

Correspondence to: John H. J. Petrini4John A. Tainer1,7 Correspondence and requests for materials should be addressed to J.A.T. (e-mail: Email: jat@scripps.edu) or J.H.J.P. (e-mail: Email: petrinij@mskcc.org). Coordinates for pfRad50-CXXC have been deposited at the Protein Data Bank under accession code 1L8D.

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The Mre11 complex (Mre11–Rad50–Nbs1) is central to chromosomal maintenance and functions in homologous recombination, telomere maintenance and sister chromatid association1, 2, 3, 4, 5, 6, 7. These functions all imply that the linked binding of two DNA substrates occurs, although the molecular basis for this process remains unknown. Here we present a 2.2 Å crystal structure of the Rad50 coiled-coil region that reveals an unexpected dimer interface at the apex of the coiled coils in which pairs of conserved Cys-X-X-Cys motifs form interlocking hooks that bind one Zn2+ ion. Biochemical, X-ray and electron microscopy data indicate that these hooks can join oppositely protruding Rad50 coiled-coil domains to form a flexible bridge of up to 1,200 Å. This suggests a function for the long insertion in the Rad50 ABC-ATPase domain8. The Rad50 hook is functional, because mutations in this motif confer radiation sensitivity in yeast and disrupt binding at the distant Mre11 nuclease interface. These data support an architectural role for the Rad50 coiled coils in forming metal-mediated bridging complexes between two DNA-binding heads. The resulting assemblies have appropriate lengths and conformational properties to link sister chromatids in homologous recombination and DNA ends in non-homologous end-joining.