Recruitment of Mre11 to recombination sites during meiosis.

The Mre11 nuclease is part of the highly conserved MRX complex involved in the repair of DNA double-strand breaks (DSBs). During meiosis in budding yeast, MRX is also required for the programmed induction of DSBs by Spo11, thereby initiating homologous recombination to promote accurate chromosome segregation. Recruitment of Mre11 to meiotic DSB sites depends on Rec114-Mei4 and Mer2 (RMM), which are thought to organize the meiotic DSB machinery by a mechanism involving biomolecular condensation. Here, we explored the role of Mre11 during meiosis and its relationship to RMM condensation. We show that both Mre11 and MRX complexes form DNA-dependent, hexanediol sensitive condensates in vitro. In vivo, Mre11 assembles into DNA damage-dependent foci in vegetative cells and DSB-independent foci in meiotic cells. In vitro condensates and in vivo foci both depend on the C-terminal intrinsically-disordered region (IDR) of Mre11. Importantly, while the Mre11 IDR is dispensable for vegetative DNA repair it is essential during meiosis. The C-terminal region of Mre11 forms a short α-helix that binds a conserved region of Mer2, and mutating residues within this interface reduces Mre11 foci and DSB formation. Finally, we identified a SUMO-interacting motif within the Mre11 IDR that enhances recruitment of Mre11 during meiosis and facilitates DSB formation. Our results provide new insights into the biophysical properties of Mre11 and its role in initiating meiotic recombination.