Recruitment of Mre11 to recombination sites during meiosis.

The Mre11 nuclease is part of the conserved MRX complex involved in DNA double-strand break (DSB) repair. During meiosis in budding yeast, MRX is also required for Spo11-mediated programmed DSB formation to initiate homologous recombination. Recruitment of Mre11 to meiotic DSB sites depends on Rec114-Mei4 and Mer2, proposed to organize the DSB machinery via biomolecular condensation. Here, we show that Mre11 and MRX complexes form DNA-dependent, hexanediol-sensitive condensates in vitro. In vivo, Mre11 assembles into DNA damage-dependent foci during mitosis and DSB-independent foci during meiosis. Both in vitro condensates and in vivo foci require Mre11 C-terminal intrinsically-disordered region (IDR). While dispensable for vegetative DNA repair, Mre11 IDR is essential during meiosis, where it mediates interaction with Mer2 via a short α-helix and contains a SUMO-interacting motif that enhances Mre11 recruitment and DSB formation. Together, these findings provide insights into the biophysical properties of Mre11 and its role in initiating meiotic recombination.