A supramodular FHA/BRCT-repeat architecture mediates Nbs1 adaptor function in response to DNA damage.
The Mre11/Rad50/Nbs1 protein complex plays central enzymatic and signaling roles in the DNA-damage response. Nuclease (Mre11) and scaffolding (Rad50) components of MRN have been extensively characterized, but the molecular basis of Nbs1 function has remained elusive. Here, we present a 2.3A crystal structure of the N-terminal region of fission yeast Nbs1, revealing an unusual but conserved architecture in which the FHA- and BRCT-repeat domains structurally coalesce. We demonstrate that diphosphorylated pSer-Asp-pThr-Asp motifs, recently identified as multicopy docking sites within Mdc1, are evolutionarily conserved Nbs1 binding targets. Furthermore, we show that similar phosphomotifs within Ctp1, the fission yeast ortholog of human CtIP, promote interactions with the Nbs1 FHA domain that are necessary for Ctp1-dependent resistance to DNA damage. Finally, we establish that human Nbs1 interactions with Mdc1 occur through both its FHA- and BRCT-repeat domains, suggesting how their structural and functional interdependence underpins Nbs1 adaptor functions in the DNA-damage response.
Division of Molecular Structure, Medical Research Council National Institute for Medical Research, The Ridgeway, Mill Hill, London, UK.
Janette
J
Lloyd
J Ross
JR
Chapman
Julie A
JA
Clapperton
Lesley F
LF
Haire
Edgar
E
Hartsuiker
Jiejin
J
Li
Antony M
AM
Carr
Stephen P
SP
Jackson
Stephen J
SJ
Smerdon
D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000737:chemistry*; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D012568:Schizosaccharomyces / Q000737:chemistry* / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry* / Q000378:metabolism; D016415:Sequence Alignment
D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; C525888:Ctp1 protein, S pombe; D004268:DNA-Binding Proteins; C112156:NBN protein, human; C478035:Nbs1 protein, S pombe; D009687:Nuclear Proteins; D029702:Schizosaccharomyces pombe Proteins