Recruitment of Mre11 to recombination sites during meiosis

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• The Mre11 nuclease, part of the MRX complex, repairs DNA double-strand breaks (DSBs) and is vital for programmed DSB induction during meiosis in budding yeast.
• Recruitment of Mre11 to meiotic DSB sites relies on the Rec114-Mei4 and Mer2 (RMM) complex, potentially involving biomolecular condensation.
• Understanding Mre11's biophysical properties and its specific role in meiosis is key to comprehending homologous recombination and chromosome segregation.

Purpose of the Study:

• To investigate the role of Mre11 during meiosis and its connection to RMM-mediated condensation.
• To elucidate the biophysical characteristics of Mre11 and MRX complexes in vitro and in vivo.
• To determine the functional significance of Mre11's intrinsically disordered region (IDR) and its interactions during meiotic recombination.

Main Methods:

• In vitro studies of Mre11 and MRX complex condensation using DNA and hexanediol.
• In vivo observation of Mre11 foci formation in vegetative and meiotic cells.
• Mutational analysis of Mre11's C-terminal region and its interaction with Mer2.
• Identification and functional assessment of a SUMO-interacting motif within 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 during meiosis.
• The C-terminal intrinsically disordered region (IDR) of Mre11 is essential for meiotic function but dispensable for vegetative DNA repair.
• A specific α-helix in Mre11's C-terminus 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 exhibits unique biophysical properties, forming DNA-dependent condensates essential for meiotic DSB induction.
• The Mre11 IDR plays a critical, meiosis-specific role in regulating Mre11 function and recruitment.
• Interactions between Mre11 and Mer2, along with SUMOylation, are crucial for initiating meiotic recombination and ensuring accurate chromosome segregation.