Recruitment of Mre11 to recombination sites during meiosis

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• The Mre11 nuclease, part of the MRX complex, repairs DNA double-strand breaks (DSBs) and initiates meiotic recombination.
• Recruitment of Mre11 to meiotic DSB sites relies on the Rec114-Mei4-Mer2 (RMM) complex, which utilizes biomolecular condensation.

Purpose of the Study:

• To investigate the role of Mre11 during meiosis and its connection to RMM condensation.
• To elucidate the mechanisms governing Mre11 recruitment and function in meiotic recombination.

Main Methods:

• In vitro studies of Mre11 and MRX complex condensation.
• In vivo analysis of Mre11 foci formation in vegetative and meiotic cells.
• Mutational analysis of Mre11's C-terminal intrinsically disordered region (IDR) and its interaction with Mer2.
• Identification of a SUMO-interacting motif in the Mre11 IDR.

Main Results:

• Mre11 and MRX complexes form DNA-dependent, hexanediol-sensitive condensates in vitro.
• Mre11 assembles into DNA damage-dependent foci in vegetative cells and DSB-independent foci in meiotic cells.
• The Mre11 IDR is essential for meiotic function but dispensable for vegetative DNA repair.
• A C-terminal alpha-helix of Mre11 binds Mer2, and mutations disrupt foci and DSB formation.
• A SUMO-interacting motif in the Mre11 IDR enhances meiotic recruitment and DSB formation.

Conclusions:

• Mre11 forms DNA-dependent condensates crucial for meiotic recombination initiation.
• The Mre11 IDR plays a critical, meiosis-specific role in DSB formation and recruitment.
• Interactions between Mre11 and Mer2, along with SUMOylation, are key mechanisms for meiotic Mre11 recruitment.