ESCRT-III assembles around mis-segregated DNA to protect genome stability

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Chromosome mis-segregation during cell division threatens genome stability.
• The abscission checkpoint (NoCut) delays cell separation when DNA bridges persist, involving the ESCRT complex.
• ESCRT-III is known for sealing the nuclear envelope during anaphase.

Purpose of the Study:

• To investigate the role of ESCRT-III in the NoCut checkpoint response to persistent DNA bridges.
• To determine if ESCRT-III directly protects DNA bridges from damage.
• To elucidate the mechanism by which ESCRT-III safeguards genome stability.

Main Methods:

• Immunofluorescence microscopy to track ESCRT-III localization.
• Depletion studies using siRNA (e.g., CHMP1B depletion) to assess DNA damage.
• In vitro assembly assays with purified ESCRT-III proteins (CHMP1B, IST1) and DNA.
• Analysis of cell division phenotypes (cytokinesis failure, binucleation) in cells with mutant CHMP1B.

Main Results:

• ESCRT-III is repurposed from the nuclear envelope to persistent DNA bridges during the NoCut response.
• Depletion of ESCRT-III components (CHMP1B) leads to increased DNA damage at bridges.
• In vitro, ESCRT-III filaments (CHMP1B/IST1) directly bind and protect DNA and nucleosomes from nucleases and cGAS.
• A DNA-binding mutant of CHMP1B causes cytokinesis failure and binucleation when DNA bridges persist.

Conclusions:

• ESCRT-III directly binds and protects persistent DNA bridges from damage during cytokinesis.
• This ESCRT-III-mediated DNA protection is a critical mechanism for maintaining genome stability.
• The NoCut checkpoint leverages ESCRT-III to prevent catastrophic DNA damage and ensure successful cell division.