InterPro domain: IPR013134

The MRN complex (Mre11-Rad50-Nbs1) plays an important role in many DNA metabolic events that involve DNA double-stranded breaks. MRN is one of the first factors to be localised to DNA lesions where it might have a structural role by tethering and stabilising broken chromosomes [ 1 , 2 ].

Rad50 is a split ABC-type ATPase; its centre contains a long heptad repeat that folds into an antiparallel coiled coil, bringing the N-terminal (Walker A) and the C-terminal (Walker B) domains in close proximity [ 3 ]. The apex of the coiled coil contains a dimerization interface, a conserved Cys-X-X-Cys motif in a hook-shaped domain that dimerizes with a second hook domain via cysteine-mediated zinc ion coordination. This zinc dependent dimerization event allows the formation of a complex that has appropriate lengths and conformational proporties to link sister chromatids in homologous recombination and DNA ends in non-homologous end-joining.

1. The MRN complex: coordinating and mediating the response to broken chromosomes. EMBO Rep. 4, 844-9
2. Human Rad50/Mre11 is a flexible complex that can tether DNA ends. Mol. Cell 8, 1129-35
3. The Rad50 zinc-hook is a structure joining Mre11 complexes in DNA recombination and repair. Nature 418, 562-6