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Updated: May 10, 2026

Assessment of Global DNA Double-Strand End Resection using BrdU-DNA Labeling coupled with Cell Cycle Discrimination Imaging
Published on: April 28, 2021
On the mechanism of recombination hotspot scanning during double-stranded DNA break resection
Carolina Carrasco1, Neville S Gilhooly, Mark S Dillingham
1Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientificas, 28049 Cantoblanco, Madrid, Spain.
Abstract:
Double-stranded DNA break repair by homologous recombination is initiated by resection of free DNA ends to produce a 3'-ssDNA overhang. In bacteria, this reaction is catalyzed by helicase-nuclease complexes such as AddAB in a manner regulated by specific recombination hotspot sequences called Crossover hotspot instigator (Chi). We have used magnetic tweezers to investigate the dynamics of AddAB translocation and hotspot scanning during double-stranded DNA break resection. AddAB was prone to stochastic pausing due to transient recognition of Chi-like sequences, unveiling an antagonistic relationship between DNA translocation and sequence-specific DNA recognition. Pauses at bona fide Chi sequences were longer, were nonexponentially distributed, and resulted in an altered velocity upon restart of translocation downstream of Chi. We propose a model for the recognition of Chi sequences to explain the origin of pausing during failed and successful hotspot recognition.
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