Nbs1 flexibly tethers Ctp1 and Mre11-Rad50 to coordinate DNA double-strand break processing and repair

Cell. 2009 Oct 2;139(1):87-99. doi: 10.1016/j.cell.2009.07.033.

Abstract

The Nijmegen breakage syndrome 1 (Nbs1) subunit of the Mre11-Rad50-Nbs1 (MRN) complex protects genome integrity by coordinating double-strand break (DSB) repair and checkpoint signaling through undefined interactions with ATM, MDC1, and Sae2/Ctp1/CtIP. Here, fission yeast and human Nbs1 structures defined by X-ray crystallography and small angle X-ray scattering (SAXS) reveal Nbs1 cardinal features: fused, extended, FHA-BRCT(1)-BRCT(2) domains flexibly linked to C-terminal Mre11- and ATM-binding motifs. Genetic, biochemical, and structural analyses of an Nbs1-Ctp1 complex show Nbs1 recruits phosphorylated Ctp1 to DSBs via binding of the Nbs1 FHA domain to a Ctp1 pThr-Asp motif. Nbs1 structures further identify an extensive FHA-BRCT interface, a bipartite MDC1-binding scaffold, an extended conformational switch, and the molecular consequences associated with cancer predisposing Nijmegen breakage syndrome mutations. Tethering of Ctp1 to a flexible Nbs1 arm suggests a mechanism for restricting DNA end processing and homologous recombination activities of Sae2/Ctp1/CtIP to the immediate vicinity of DSBs.

Publication types

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

MeSH terms

  • Acid Anhydride Hydrolases
  • Cell Cycle Proteins / chemistry*
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Chromosomal Proteins, Non-Histone / chemistry*
  • Chromosomal Proteins, Non-Histone / genetics
  • Chromosomal Proteins, Non-Histone / metabolism
  • Crystallography, X-Ray
  • DNA Repair Enzymes / metabolism
  • DNA Repair*
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / metabolism
  • Humans
  • MRE11 Homologue Protein
  • Models, Molecular
  • Mutation
  • Nuclear Proteins / chemistry*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Protein Structure, Tertiary
  • Scattering, Small Angle
  • Schizosaccharomyces / metabolism
  • Schizosaccharomyces pombe Proteins / chemistry*
  • Schizosaccharomyces pombe Proteins / genetics
  • Schizosaccharomyces pombe Proteins / metabolism

Substances

  • Cell Cycle Proteins
  • Chromosomal Proteins, Non-Histone
  • Ctp1 protein, S pombe
  • DNA-Binding Proteins
  • MRE11 protein, human
  • NBN protein, human
  • Nbs1 protein, S pombe
  • Nuclear Proteins
  • Schizosaccharomyces pombe Proteins
  • MRE11 Homologue Protein
  • Acid Anhydride Hydrolases
  • Rad50 protein, human
  • DNA Repair Enzymes