Abnormal kinetochore structure activates the spindle assembly checkpoint in budding yeast

Area of Science:

• Cell Biology
• Genetics
• Molecular Biology

Background:

• Kinetochore function is crucial for accurate chromosome segregation during cell division.
• Failures in chromosome attachment to the spindle can lead to cell cycle delays.
• Budding yeast provides a model system to study conserved cell cycle regulation.

Purpose of the Study:

• To investigate the role of kinetochore integrity in cell cycle progression.
• To identify conserved surveillance pathways that monitor chromosome attachment.
• To determine the involvement of spindle assembly checkpoint genes in kinetochore-mediated delays.

Main Methods:

• Generating kinetochore defects using centromere DNA mutations (CDEII delta 31) and kinetochore protein mutations (ctf13-30) in Saccharomyces cerevisiae.
• Assessing anaphase entry delays in mutant strains.
• Analyzing the requirement of spindle assembly checkpoint genes (MAD2, BUB1, BUB2) and DNA damage checkpoint gene (RAD9) in these delays.
• Evaluating chromosome missegregation rates in relevant mutants.

Main Results:

• Abnormal kinetochores induce a preanaphase delay, similar to observations in animal cells.
• Genes MAD2 and BUB1 are essential for establishing and/or maintaining kinetochore-induced delays.
• BUB2 is important for maintaining the delay, while RAD9 is not involved.
• Loss of MAD2 or BUB1 function leads to increased chromosome missegregation, highlighting the delay's role in fidelity.

Conclusions:

• Abnormal kinetochore structures activate conserved spindle assembly checkpoint functions to induce preanaphase delay.
• This pathway is critical for ensuring chromosome transmission fidelity.
• The findings suggest a conserved mechanism for monitoring chromosome attachment across eukaryotes.