The DNA Replication Checkpoint Targets the Kinetochore for Relocation of Collapsed Forks to the Nuclear Periphery

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Expanded CAG/CTG repeats form hairpin structures that impede DNA replication, leading to fork collapse.
• These problematic DNA structures are known to relocate to the nuclear pore complex (NPC).
• The DNA damage checkpoint is activated by stalled replication forks.

Purpose of the Study:

• To investigate the role of DNA replication checkpoint proteins in the relocation of collapsed forks in *S. cerevisiae*.
• To determine if checkpoint activation is necessary for moving stalled replication forks to the nuclear periphery.

Main Methods:

• Utilized *S. cerevisiae* as a model organism.
• Investigated the relocation of a (CAG/CTG)₁₃₀ tract.
• Assessed the dependence on the Mrc1/Rad53 replication checkpoint and Cep3 phosphorylation.

Main Results:

• Relocation of the (CAG/CTG)₁₃₀ tract to the nuclear periphery requires the Mrc1/Rad53 replication checkpoint.
• Checkpoint-mediated phosphorylation of Cep3 is essential for centromere detachment and fork relocation.
• DNA damage induces microtubule recruitment to the repeat locus, facilitating movement.

Conclusions:

• The DNA replication checkpoint plays a crucial role in repositioning collapsed replication forks to the nuclear periphery.
• Centromere release and microtubule-directed motion are key mechanisms involved in this process.
• This study establishes a novel function for the DNA replication and damage checkpoints in managing challenging DNA repeat structures.