Meiotic Centromere Coupling and Pairing Function by Two Separate Mechanisms in Saccharomyces cerevisiae

Area of Science:

• Cell Biology
• Genetics
• Molecular Biology

Background:

• During meiosis I, homologous chromosomes pair and segregate.
• In Saccharomyces cerevisiae, centromeres associate via homology-independent centromere coupling and homology-dependent centromere pairing.
• The synaptonemal complex protein Zip1 is crucial for both centromere coupling and pairing.

Purpose of the Study:

• To investigate the role of centromere coupling in modulating centromere-proximal recombination.
• To determine if centromere coupling and centromere pairing share genetic requirements.
• To assess the roles of other synaptonemal complex proteins (Ecm11, Zip4) in centromere pairing.

Main Methods:

• Utilized the zip1-S75E mutant, which specifically disrupts centromere coupling.
• Analyzed centromere-proximal recombination rates in the presence and absence of centromere coupling.
• Assessed centromere pairing and chromosome segregation in mutants lacking Ecm11 and Zip4.

Main Results:

• The zip1-S75E mutation did not alter centromere-proximal recombination.
• Centromere coupling is genetically distinct from centromere pairing.
• Ecm11 is dispensable for centromere pairing and segregation of achiasmate chromosomes.
• Zip4 is not required for pachytene centromere pairing but is essential for proper segregation of achiasmate chromosomes.

Conclusions:

• Centromere coupling and pairing are distinct meiotic processes with different genetic underpinnings.
• Centromere pairing is necessary but not sufficient for ensuring the disjunction of achiasmate chromosomes.
• Synaptonemal complex proteins Zip1, Ecm11, and Zip4 exhibit differential roles in centromere interactions and chromosome segregation during meiosis.