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The RAD6 DNA damage tolerance pathway operates uncoupled from the replication fork and is functional beyond S phase
Georgios I Karras1, Stefan Jentsch
1Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
Cell
|April 21, 2010
Summary
DNA damage tolerance pathways, RAD6 and translesion synthesis (TLS), function effectively in G2/M phase, not just S phase. This suggests they act on single-stranded gaps after replication restarts.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- DNA damage poses a significant threat to genome stability by obstructing DNA replication forks.
- The RAD6 pathway, involving PCNA ubiquitylation, is crucial for DNA damage tolerance in eukaryotes.
- This pathway has two branches: error-prone translesion synthesis (TLS) and an error-free pathway, both traditionally thought to operate during S phase.
Purpose of the Study:
- To investigate the cell-cycle phase dependency of the RAD6 pathway's DNA damage tolerance mechanisms.
- To determine if limiting TLS or the error-free pathway to G2/M phase impacts lesion tolerance.
Main Methods:
- Experimental manipulation of translesion synthesis (TLS) and error-free DNA damage tolerance pathways.
- Cell-cycle phase synchronization and analysis.
- Assessment of lesion tolerance efficacy.
Main Results:
- Limiting either TLS or the error-free pathway to the G2/M phase significantly enhanced DNA lesion tolerance.
- Both branches of the RAD6 pathway were found to be effective outside of the S phase, specifically in G2/M.
- This indicates a broader role for these pathways beyond immediate replication completion.
Conclusions:
- The RAD6 pathway's DNA damage tolerance mechanisms, including TLS and the error-free pathway, operate effectively after chromosomal replication, in the G2/M phase.
- These pathways likely act on single-stranded gaps that arise behind re-initiated replication forks.
- Findings challenge the traditional view of these pathways being exclusively confined to S phase for ensuring replication completion.
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