Structure
Volume 24, Issue 8, 2 August 2016, Pages 1292-1300
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Article
Active Control of Repetitive Structural Transitions between Replication Forks and Holliday Junctions by Werner Syndrome Helicase

https://doi.org/10.1016/j.str.2016.06.004Get rights and content
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Highlights

  • The fork regression of WRN is readily activated after lagging arm unwinding

  • WRN migrates a Holliday junction with 3.2 ± 0.03 bases/s velocity

  • WRN reverses branch migration direction at short heterologous sequences

  • The branch migration reversal of WRN is an active process

Summary

The reactivation of stalled DNA replication via fork regression invokes Holliday junction formation, branch migration, and the recovery of the replication fork after DNA repair or error-free DNA synthesis. The coordination mechanism for these DNA structural transitions by molecular motors, however, remains unclear. Here we perform single-molecule fluorescence experiments with Werner syndrome protein (WRN) and model replication forks. The Holliday junction is readily formed once the lagging arm is unwound, and migrated unidirectionally with 3.2 ± 0.03 bases/s velocity. The recovery of the replication fork was controlled by branch migration reversal of WRN, resulting in repetitive fork regression. The Holliday junction formation, branch migration, and migration direction reversal are all ATP dependent, revealing that WRN uses the energy of ATP hydrolysis to actively coordinate the structural transitions of DNA.

Keywords

werner syndrome helicase
single-molecule FRET
replication fork regression

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