Molecular Cell
Volume 67, Issue 5, 7 September 2017, Pages 882-890.e5
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Short Article
Replication Fork Slowing and Reversal upon DNA Damage Require PCNA Polyubiquitination and ZRANB3 DNA Translocase Activity

https://doi.org/10.1016/j.molcel.2017.08.010Get rights and content
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Highlights

  • Fork slowing and reversal upon damage require K63-linked PCNA polyubiquitination

  • ZRANB3 mediates fork slowing/reversal in vivo via binding to polyubiquitinated PCNA

  • ZRANB3 DNA translocase—not nuclease—activity mediates fork slowing and reversal

  • Mammalian error-free postreplication repair entails global fork slowing and reversal

Summary

DNA damage tolerance during eukaryotic replication is orchestrated by PCNA ubiquitination. While monoubiquitination activates mutagenic translesion synthesis, polyubiquitination activates an error-free pathway, elusive in mammals, enabling damage bypass by template switching. Fork reversal is driven in vitro by multiple enzymes, including the DNA translocase ZRANB3, shown to bind polyubiquitinated PCNA. However, whether this interaction promotes fork remodeling and template switching in vivo was unknown. Here we show that damage-induced fork reversal in mammalian cells requires PCNA ubiquitination, UBC13, and K63-linked polyubiquitin chains, previously involved in error-free damage tolerance. Fork reversal in vivo also requires ZRANB3 translocase activity and its interaction with polyubiquitinated PCNA, pinpointing ZRANB3 as a key effector of error-free DNA damage tolerance. Mutations affecting fork reversal also induced unrestrained fork progression and chromosomal breakage, suggesting fork remodeling as a global fork slowing and protection mechanism. Targeting these fork protection systems represents a promising strategy to potentiate cancer chemotherapy.

Keywords

DNA damage tolerance
replication fork reversal
replication fork progression
cancer chemotherapeutics
PCNA ubiquitination
postreplication repair
ZRANB3 DNA translocase
electron microscopy in vivo
single-molecule approaches

Cited by (0)

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Present address: Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institut, Villigen-PSI, Switzerland

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