Feedback control of chromosome separation by a midzone Aurora B gradient

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Accurate chromosome segregation is crucial for cell division, requiring sister chromatid separation before nuclear envelope reassembly (NER).
• The coordination between chromosome separation and NER remains poorly understood.

Purpose of the Study:

• To identify the regulatory mechanisms coordinating chromosome segregation and nuclear envelope reassembly during mitosis.
• To elucidate how cells ensure complete sister chromatid separation before proceeding to chromosome decondensation and NER.

Main Methods:

• Investigated a conserved feedback control mechanism involving Aurora B kinase and phosphatases PP1/PP2A.
• Analyzed the role of an Aurora B gradient at the midzone in monitoring chromosome position.
• Assessed the impact of Aurora B on Condensin I retention and its effect on chromosome decondensation and NER.

Main Results:

• Identified a feedback mechanism that delays chromosome decondensation and NER when chromosome separation is incomplete.
• Demonstrated that a midzone Aurora B gradient monitors chromosome position and retains Condensin I, preventing premature decondensation.
• Showed that PP1/PP2A phosphatases counteract the Aurora B gradient, promoting decondensation and NER.

Conclusions:

• An Aurora B gradient-mediated surveillance mechanism ensures effective sister chromatid separation before chromosome decondensation and NER.
• This system allows for the correction of lagging chromosomes, integrating them into the main nuclei before NER completion.
• The findings reveal a critical coordination step ensuring genomic integrity during cell division.