ATR protects centromere identity by promoting DAXX association with PML nuclear bodies

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Centromere protein A (CENP-A) is crucial for centromere identity and kinetochore assembly, ensuring accurate chromosome segregation.
• The ataxia telangiectasia and Rad3-related (ATR) kinase is a key regulator of the DNA damage response.
• Promyelocytic leukemia nuclear bodies (PML NBs) are nuclear structures involved in various cellular processes and house specific protein chaperones.

Purpose of the Study:

• To investigate the role of ATR kinase in maintaining CENP-A occupancy at interphase centromeres.
• To elucidate the mechanism by which ATR influences CENP-A localization and centromere identity.
• To determine the consequences of ATR inhibition on centromere function and genome stability.

Main Methods:

• Immunofluorescence microscopy to visualize ATR, DAXX, and CENP-A localization.
• Biochemical assays to assess protein-protein interactions and phosphorylation.
• Cell-based assays to evaluate kinetochore formation and chromosome segregation fidelity.

Main Results:

• ATR kinase localizes to PML NBs in unperturbed cells, associating with the histone chaperone DAXX.
• ATR inhibition disrupts DAXX association with PML NBs, leading to DAXX-dependent CENP-A loss and increased H3.3 at centromeres.
• ATR-dependent phosphorylation of DAXX is critical for CENP-A maintenance and DAXX localization.
• Acute ATR inhibition causes kinetochore defects and increased lagging chromosomes during mitosis.

Conclusions:

• ATR kinase plays a critical, DNA damage-independent role in safeguarding CENP-A occupancy at interphase centromeres.
• ATR signaling pathway, through DAXX, is essential for maintaining centromere identity and preventing genome instability.
• These findings reveal a novel mechanism linking ATR kinase activity to centromere function and overall genomic integrity.