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J Mol Biol August 29, 2008; 381 (2): 361-72.
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Structure of a second BRCT domain identified in the nijmegen breakage syndrome protein Nbs1 and its function in an MDC1-dependent localization of Nbs1 to DNA damage sites.

Xu C , Wu L , Cui G , Botuyan MV , Chen J , Mer G .

The Nijmegen breakage syndrome protein Nbs1 is a component of the MRN (Mre11-Rad50-Nbs1) complex, central to the DNA damage response. While Nbs1 is generally believed to encompass a forkhead-associated domain linked to a breast cancer C-terminal (BRCT) domain, to date there is no experimental information on its three-dimensional structure. Through nuclear magnetic resonance (NMR) three-dimensional structure determination, we demonstrate that there is a second BRCT domain (BRCT2) in Nbs1. The domain has the characteristic BRCT topology, but with a long insertion shown to be flexible by NMR relaxation measurements. In the absence of sequence similarity to other proteins, a search for structural analogs of BRCT2 returned the second BRCT domain of the tandem BRCT repeats of cell cycle checkpoint proteins MDC1 (mediator of DNA damage checkpoint protein 1) and BRCA1 (breast cancer protein 1), suggesting that like MDC1 and BRCA1, Nbs1 also possesses tandem BRCT domains with phosphoprotein binding ability. Structure-based single point mutations in human Nbs1 were evaluated in vivo and revealed that BRCT2 is essential for an MDC1-dependent relocalization of Nbs1 to DNA damage sites, most likely through a direct interaction of Nbs1 tandem BRCT domains with phosphorylated MDC1.

PubMed ID: 18582474
PMC ID: PMC2574983
Article link: J Mol Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: brca1 mdc1 mre11 nbn rad50

References [+] :
Bashford, Generalized born models of macromolecular solvation effects. 2000, Pubmed