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Mechanism of DNA End Sensing and Processing by the Mre11-Rad50 Complex.

Molecular cell (2019-09-08)
Lisa Käshammer, Jan-Hinnerk Saathoff, Katja Lammens, Fabian Gut, Joseph Bartho, Aaron Alt, Brigitte Kessler, Karl-Peter Hopfner
ABSTRACT

DNA double-strand breaks (DSBs) threaten genome stability throughout life and are linked to tumorigenesis in humans. To initiate DSB repair by end joining or homologous recombination, the Mre11-nuclease Rad50-ATPase complex detects and processes diverse and obstructed DNA ends, but a structural mechanism is still lacking. Here we report cryo-EM structures of the E. coli Mre11-Rad50 homolog SbcCD in resting and DNA-bound cutting states. In the resting state, Mre11's nuclease is blocked by ATP-Rad50, and the Rad50 coiled coils appear flexible. Upon DNA binding, the two coiled coils zip up into a rod and, together with the Rad50 nucleotide-binding domains, form a clamp around dsDNA. Mre11 moves to the side of Rad50, binds the DNA end, and assembles a DNA cutting channel for the nuclease reactions. The structures reveal how Mre11-Rad50 can detect and process diverse DNA ends and uncover a clamping and gating function for the coiled coils.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Adenosine 5′-[γ-thio]triphosphate tetralithium salt, ≥75% (HPLC), powder
Sigma-Aldrich
Adenosine 5′-triphosphate disodium salt hydrate, Grade II, ≥97% (HPLC), crystalline, from microbial