Holliday junction-ZMM protein feedback enables meiotic crossover assurance

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Holliday junctions (HJs) are critical DNA structures in homologous recombination and chromosome segregation during meiosis.
• While HJs are essential for crossing-over, their precise regulatory roles beyond repair remain incompletely understood.
• Accumulation of HJs during meiotic prophase I poses risks to chromosome segregation.

Purpose of the Study:

• To investigate the regulatory functions of Holliday junctions (HJs) in meiosis.
• To elucidate the mechanism by which HJs influence synaptonemal complex dynamics and chromosome structure.
• To understand how HJs impact recombination pathways and prevent DNA damage during meiotic progression.

Main Methods:

• Development of a conditional nucleolytic resolution system for HJs in budding yeast.
• Analysis of synaptonemal complex disassembly and chromosome organization following HJ resolution.
• Investigation of the interaction between HJs, ZMM proteins, and recombination nodules.

Main Results:

• HJ resolution triggers complete synaptonemal complex disassembly without disrupting chromosome axis-loop organization.
• HJs facilitate the association of ZMM proteins with recombination nodules, promoting synaptonemal complex polymerization.
• The interplay between HJs and ZMM proteins stabilizes synaptonemal complex structure, suppresses new double-strand breaks, and prevents recombination reinitiation.

Conclusions:

• Holliday junctions play a crucial regulatory role in maintaining meiotic chromosome synapsis through feedback with ZMM proteins.
• This HJ-ZMM interaction is essential for suppressing DNA damage responses and ensuring crossover assurance during meiosis.
• The findings reveal a novel mechanism by which HJs contribute to genome stability and successful meiotic progression.