Nbs1 Flexibly Tethers Ctp1 and Mre11-Rad50 to Coordinate DNA Double-Strand Break Processing and Repair

• Published in: Cell Vol. 139; no. 1; pp. 87 - 99
• Main Authors: Williams, R. Scott, Dodson, Gerald E., Limbo, Oliver, Yamada, Yoshiki, Williams, Jessica S., Guenther, Grant, Classen, Scott, Glover, J.N. Mark, Iwasaki, Hiroshi, Russell, Paul, Tainer, John A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 02.10.2009
• Subjects: 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; DISEASE; DNA; DNA Repair; DNA Repair Enzymes - metabolism; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - metabolism; Humans; Models, Molecular; MRE11 Homologue Protein; Mutation; Nuclear Proteins - chemistry; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Protein Structure, Tertiary; PROTEINS; Scattering, Small Angle; Schizosaccharomyces - metabolism; Schizosaccharomyces pombe; Schizosaccharomyces pombe Proteins - chemistry; Schizosaccharomyces pombe Proteins - genetics; Schizosaccharomyces pombe Proteins - metabolism; PROTEINS; DNA; DISEASE
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2009.07.033

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.