Distinct chromatin regulators downmodulate meiotic axis formation and DNA break induction at chromosome ends

Area of Science:

• Genetics
• Molecular Biology
• Chromatin Biology

Background:

• Meiotic crossover recombination is essential for accurate chromosome segregation.
• Recombination is typically suppressed near chromosome ends in many organisms.
• The molecular mechanisms underlying this telomeric suppression are not fully understood.

Purpose of the Study:

• To identify and characterize chromatin modifiers regulating meiotic recombination suppression at chromosome ends in *Saccharomyces cerevisiae*.
• To elucidate the roles of Dot1 and the Sir complex in controlling recombination axis proteins and DNA double-strand break formation at telomeres.

Main Methods:

• Quantitative analysis of recombination-promoting axis proteins (Red1, Hop1) and cohesin (Rec8) distribution near telomeres.
• Investigating the function of histone methyltransferase Dot1 in directing axis protein binding.
• Assessing the role of the Sir silencing complex in suppressing meiotic DNA double-strand breaks (DSBs) at chromosome ends.
• Analyzing the relationship between Sir complex activity, transcriptional silencing, and DSB formation.

Main Results:

• Recombination-promoting axis proteins Red1 and Hop1 are reduced near telomeres, while Rec8 levels remain unchanged.
• Dot1 is crucial for maintaining the reduced levels of Red1 and Hop1 at chromosome interiors.
• The Sir complex suppresses meiotic DSBs at chromosome ends in a manner dependent on its spreading and silencing activity.
• Sir-mediated DSB suppression is independent of axis protein deposition and targets promoter regions.

Conclusions:

• Multiple, distinct chromatin-based mechanisms collaborate to ensure robust suppression of meiotic recombination near chromosome ends.
• Dot1 regulates axis protein distribution, while the Sir complex controls DSB formation via transcriptional silencing.
• These findings provide a comprehensive understanding of telomeric recombination regulation in *Saccharomyces cerevisiae*.