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Updated: Jun 13, 2026
10:32
Detection of Post-Replicative Gaps Accumulation and Repair in Human Cells Using the DNA Fiber Assay
Published on: February 3, 2022
Postreplication gaps at UV lesions are signals for checkpoint activation.
A John Callegari1, Emily Clark, Amanda Pneuman
1Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Summary
UV light triggers a cell cycle delay, signaling DNA repair needs. Fission yeast studies reveal translesion DNA polymerases Polkappa and Poleta are key to this checkpoint response, acting on postreplication DNA gaps.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Eukaryotic cells activate a checkpoint response delaying cell-cycle progression upon UV light exposure.
- This checkpoint is hypothesized to signal DNA damage structures encountered by replication forks.
- Translesion DNA polymerases are crucial for navigating DNA damage during replication.
Purpose of the Study:
- To investigate the role of translesion DNA polymerases in the UV-induced DNA damage checkpoint response.
- To identify the specific structures that signal checkpoint activation after UV irradiation.
- To elucidate the mechanism by which DNA damage signaling and repair are coordinated.
Main Methods:
- Time-lapse microscopy in Schizosaccharomyces pombe (fission yeast).
- Genetic analysis of translesion DNA polymerase mutants (Polkappa, Poleta, Rev1, Polzeta).
- Quantitative flow cytometry to assess DNA replication rates.
Main Results:
- Disruption of Polkappa and Poleta genes significantly prolonged the UV checkpoint response.
- Cells lacking Polkappa or Poleta showed prolonged checkpoint activation, indicating their substrates are checkpoint signals.
- No evidence found that Rev1 or Polzeta repair checkpoint-recognized structures.
- Replication rates of UV-damaged DNA were similar in mutant and wild-type cells.
Conclusions:
- Postreplication DNA gaps containing unrepaired UV lesions serve as substrates for translesion polymerases.
- These DNA gaps also function as signals that activate the cell cycle checkpoint.
- Polkappa and Poleta play a critical role in processing these gaps and modulating the checkpoint response.
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