title: The Rad50 zinc-hook is a structure joining Mre11 complexes in DNA recombination and repair.
abstract: The Mre11 complex (Mre11 Rad50 Nbs1) is central to chromosomal maintenance and functions in homologous recombination, telomere maintenance and sister chromatid association. 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 A 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 Zn(2+) 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 A. This suggests a function for the long insertion in the Rad50 ABC-ATPase domain. 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.
authors.affiliation: [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.
authors.forename: Karl-Peter
authors.initials: KP
authors.lastname: Hopfner
authors.forename: Lisa
authors.initials: L
authors.lastname: Craig
authors.forename: Gabriel
authors.initials: G
authors.lastname: Moncalian
authors.forename: Robert A
authors.initials: RA
authors.lastname: Zinkel
authors.forename: Takehiko
authors.initials: T
authors.lastname: Usui
authors.forename: Barbara A L
authors.initials: BA
authors.lastname: Owen
authors.forename: Annette
authors.initials: A
authors.lastname: Karcher
authors.forename: Brendan
authors.initials: B
authors.lastname: Henderson
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Bodmer
authors.forename: Cynthia T
authors.initials: CT
authors.lastname: McMurray
authors.forename: James P
authors.initials: JP
authors.lastname: Carney
authors.forename: John H J
authors.initials: JH
authors.lastname: Petrini
authors.forename: John A
authors.initials: JA
authors.lastname: Tainer
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair; D004268:DNA-Binding Proteins; D019281:Dimerization; D004706:Endodeoxyribonucleases / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D005090:Exodeoxyribonucleases / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D008854:Microscopy, Electron; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011836:Radiation Tolerance / Q000235:genetics; D011995:Recombination, Genetic / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D015032:Zinc / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C086930:RAD50 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; C094191:MRE11 protein, S cerevisiae; D000251:Adenosine Triphosphatases; D015032:Zinc; D003545:Cysteine