Year: 2026
Type: preprint
Abstract: Replication fork reversal is a DNA damage tolerance mechanism important for genome stability that entails annealing of parental DNA to push the fork backwards. F-box helicase 1 (FBH1) is a 3′–5′ ssDNA translocase and SCF (SKP–CUL1–F box) E3 ubiquitin ligase that catalyzes fork reversal and limits aberrant recombination, yet how its helicase activity drives strand annealing is unknown. Here, using single-molecule and biochemical assays, we show that SCF FBH1 reverses forks through a two-stage reaction in which translocation on the lagging strand template while remaining affixed at the junction destabilizes the leading strand duplex to ultimately displace the nascent leading strand. Reversal is force-sensitive and does not generate a four-way junction, revealing an annealing-independent mechanism distinct from those of SMARCAL1, HLTF, and ZRANB3. These results establish the importance of nascent strand unwinding to fork reversal and suggest the existence of distinct pathways that produce unique DNA structures, which has implications for fork restart and its measurement in cells.
Language: English
Topic: DNA Repair Mechanisms
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
Awards: G1188944981, G2212489884, Molecular Biophysics Training Grant at Vanderbilt, G2606259684, G4045293325, G410571670, G451917667, G4572625685, G4844356218, G4925834383, G523076202, G5539308778, G5967599077, G6033112984, G6384254145, G9000352068, Structural Cell Biology of DNA Repair Machines, The DNA replication-repair interface: mechanisms and regulation
OpenAlex ID: W7163911411