Protection of double-Holliday junctions ensures crossing over during meiosis

Area of Science:

• Cell Biology
• Genetics
• Molecular Biology

Background:

• Chromosomal linkages via crossover recombination are vital for homologous chromosome segregation during meiosis.
• The synaptonemal complex (SC) is a meiosis-specific structure mediating homolog synapsis and is implicated in crossover formation, but its precise role is unclear.

Purpose of the Study:

• To elucidate the role of the synaptonemal complex (SC) in promoting crossover-specific resolution of double-Holliday junctions (dHJs).
• To investigate the interdependence between SC components and crossover recombination complexes (CRCs).

Main Methods:

• Conditional inactivation of key SC components during the pachytene stage of meiosis.
• Analysis of dHJ resolution pathways, including the Sgs1-Top3-Rmi1 (STR) complex.
• Assessment of the roles of cohesin and Zip1 in maintaining SCs and CRCs.

Main Results:

• Conditional SC component inactivation leads to dHJ resolution into noncrossover products by the STR complex.
• Cohesin is essential for maintaining SCs and CRCs during pachytene.
• Zip1 maintains CRCs, and SC stability requires CRCs, highlighting an interdependence.

Conclusions:

• The SC facilitates crossover-specific dHJ resolution by preventing aberrant resolution pathways.
• Hierarchical and interdependent functions of SC components (cohesin, Zip1) and CRCs are crucial for ensuring homologous chromosome linkage and segregation.
• This study uncovers an unexpected interdependence between SC stability and the presence of CRCs.