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Lookup NU author(s): Dr Charles WinterhalterORCiD, Dr Kathy StrattonORCiD, Dr Stepan FenykORCiD, Professor Heath MurrayORCiD
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DNA damage occurs in all cells and must be repaired to maintain genome integrity. Many DNA lesions are targeted for removal by repair systems that excise the damage, thereby generating a temporary single-strand discontinuity in the chromosome. If DNA repair has not been completed prior to a round of genome duplication, the single-strand discontinuity (nick or gap) can be converted to a double-strand break (DSB) by an oncoming replication fork. Because the genomic location of nucleobase damage is stochastic, investigating the fate of replication machinery (replisome) at DNA repair sites with single-strand discontinuities has been limited. Here we have addressed this issue by expressing Cas9 nickases in Bacillus subtilis to create site specific single-strand discontinuities in a bacterial chromosome. We find that a nick in either leading or lagging strand arrests DNA replication, while the fate of the replicative helicase is distinct and depends upon the strand nicked. Genetic, biochemical, and single cell analyses indicate that replisome/nick encounters generate a single-end DSB which requires recombinational repair to enable PriA-dependent replication restart. Together this work defines the physiologically relevant pathway used by B. subtilis to reinitiate DNA synthesis following replication fork inactivation at a single-strand discontinuity.
Author(s): Winterhalter C, Stratton KJ, Fenyk S, Murray H
Publication type: Article
Publication status: Submitted
Journal: bioRxiv
Year: 2025
Acceptance date: 25/10/2025
Publisher: Cold Spring Harbor Laboratory
URL: https://www.biorxiv.org/content/10.1101/2025.02.28.640380v2
Notes: This article is a preprint and has not been certified by peer review. Submitted to Nature Communications.
