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#Mre11

2 public questions tagged with this topic.

Recombination

Primary function of MRX complex is

Efficient homologous recombination depends on conversion of blunt double-strand breaks into 3' single-stranded overhangs suitable for Rad51 filament formation. MRX and Sae2 initiate this resection by Mre11 introducing endonucleolytic nick distal to 5' blocked ends such as Spo11 adducts or Ku-bound ends. Nick creation allows bidirectional exonucleolytic degradation, primarily 5'→3' by Exo1 or Sgs1-Dna2 in extended resection. This step commits cell to homology-directed repair because long 3' tails incompatible with NHEJ. Thus MRX does not perform strand invasion or direct ligation but provides substrate for homology search.

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 12: MRX Initiated 5' Strand Resection Mechanism

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Recombination

MRX complex is composed of

In Saccharomyces cerevisiae, initial DSB processing requires trimeric Mre11-Rad50-Xrs2 complex, whose mammalian counterpart is MRN containing Nbs1 instead of Xrs2. Mre11 is nuclease with both endonuclease and 3'→5' exonuclease activities, Rad50 is long coiled-coil SMC-like protein dimerizing via zinc-hook at apex and binding ATP to undergo conformational switching between open and closed states, Xrs2/Nbs1 mediates protein interactions, nuclear localization, and Tel1/ATM checkpoint signaling. Together they sense Spo11 blocks, tether DNA ends, activate checkpoint, and initiate resection together with Sae2/CtIP, bridging structural maintenance and enzymatic nucleolysis.

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 5: MRX Complex Composition Mre11 Rad50 Xrs2

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