CENP-A chromatin prevents replication stress at centromeres to avoid structural aneuploidy

Area of Science:

• Cell Biology
• Genetics
• Epigenetics

Background:

• Centromeres are essential for chromosome segregation but their repetitive DNA is vulnerable to rearrangements.
• Factors maintaining centromere integrity and preventing translocations are largely unknown.

Purpose of the Study:

• To investigate the role of the centromere-specific histone H3 variant CENP-A in maintaining centromere integrity during DNA replication.
• To understand how CENP-A prevents aberrant DNA replication and chromosome translocations at centromeres.

Main Methods:

• Depletion of CENP-A specifically during S phase.
• Analysis of R-loop accumulation, centromeric transcription, and replication fork progression.
• Assessment of recombination, DNA breakage, and chromosome translocations at centromeric alpha-satellite DNA.

Main Results:

• Rapid CENP-A removal in S phase led to R-loop accumulation and increased centromeric transcripts.
• Replication without CENP-A impaired replication fork progression and caused unfinished replication.
• Recombination at alpha-satellites, anaphase bridges, chromosome breakage, and translocations were observed in a CENP-A-dependent manner.

Conclusions:

• CENP-A is vital for safeguarding DNA replication of alpha-satellite repeats during S phase.
• Loss of CENP-A promotes R-loop formation and recombination, leading to centromeric instability and structural aneuploidy.
• Specialized centromeric chromatin, exemplified by CENP-A, is critical for maintaining the integrity of transcribed repetitive DNA.