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Updated: Jun 13, 2026
07:27
Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase
Published on: April 29, 2010
Two fork protection complexes at the replication fork play distinct roles in fork progression and stress response
Tatiana Moiseeva1, Sameera Vipat2, Rohan Harolikar1,2
1Department of Chemistry and Biotechnology, Tallinn University of Technology, Tallinn, 12618, ESTONIA.
Research Square
|June 12, 2026
Summary
The Fork Protection Complex (FPC), including TIMELESS, has two distinct roles at replication forks. One FPC instance regulates fork speed, while another mediates checkpoint signaling for genome stability.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- The Fork Protection Complex (FPC), comprising TIMELESS, TIPIN, and CLASPIN, is crucial for DNA replication and genome stability.
- Existing models place TIMELESS at the CMG helicase's leading edge, which conflicts with FPC's known roles.
Purpose of the Study:
- To investigate the precise localization and function of the FPC during DNA replication.
- To elucidate the dual roles of TIMELESS in regulating replication fork progression and checkpoint signaling.
Main Methods:
- Split-TurboID proximity labeling to determine FPC localization.
- Auxin-inducible degron system to deplete TIMELESS and analyze mutant phenotypes.
- Analysis of replication checkpoint activation and fork speed under various conditions.
Main Results:
- Evidence supports a model of stepwise FPC loading with two TIMELESS molecules per fork.
- Split-TurboID confirmed proximity of a second FPC to the lagging strand.
- TIMELESS depletion disrupted TIPIN and CLASPIN loading, but a MCM-binding mutant retained this capacity.
- The TIMELESS mutant activated checkpoints but failed to regulate fork speed.
Conclusions:
- Two distinct FPC instances exist at each replication fork: one at the leading edge for fork progression, and one at the lagging strand for checkpoint signaling.
- These dual FPC roles are essential for TIMELESS's overall function in maintaining genome stability during replication.
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