Abstract
In Escherichia coli, recF and recR are required to stabilize and maintain replication forks arrested by UV-induced DNA damage. In the absence of RecF, replication fails to recover, and the nascent lagging strand of the arrested replication fork is extensively degraded by the RecQ helicase and RecJ nuclease. recO mutants are epistatic with recF and recR with respect to recombination and survival assays after DNA damage. In this study, we show that RecO functions with RecF and RecR to protect the nascent lagging strand of arrested replication forks after UV-irradiation. In the absence of RecO, the nascent DNA at arrested replication forks is extensively degraded and replication fails to recover. The extent of nascent DNA degradation is equivalent in single, double, or triple mutants of recF, recO, or recR, and the degradation is dependent upon RecJ and RecQ functions. Because RecF has been shown to protect the nascent lagging strand from degradation, these observations indicate that RecR and RecO function with RecF to protect the same nascent strand of the arrested replication fork and are likely to act at a common point during the recovery process. We discuss these results in relation to the biochemical and cellular properties of RecF, RecO, and RecR and their potential role in loading RecA filaments to maintain the replication fork structure after the arrest of replication by UV-induced DNA damage.
Highlights
The recovery of replication in E. coli requires RecA to stabilize and maintain the integrity of replication forks after arrest by DNA lesions
Mutants lacking RecF and RecR exhibit a delayed induction of the SOS response, consistent with the idea that these genes may help stabilize the RecA filaments which are required for SOS induction [7, 13,14,15]
The amount of DNA synthesized in either recF, recR, or recO mutants was inhibited to a similar extent after this dose of UV irradiation
Summary
The recovery of replication in E. coli requires RecA to stabilize and maintain the integrity of replication forks after arrest by DNA lesions. RecF, RecO, and RecR interact with and stabilize RecA filaments bound to DNA [12], a role that would be consistent with the in vivo observation of limiting DNA degradation at the replication fork.
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