RecQ and RecJ process blocked replication forks prior to the resumption of replication in UV-irradiated Escherichia coli

The accurate recovery of replication following DNA damage and repair is critical for the maintenance of genomic integrity. In Escherichia coli, the recovery of replication following UV-induced DNA damage is dependent upon several proteins in the recF pathway, including RecF, RecO, and RecR. Two other recF pathway proteins, the RecQ helicase and the RecJ exonuclease, have been shown to affect the sites and frequencies at which illegitimate rearrangements occur following UV-induced DNA damage, suggesting that they also may function during the recovery of replication. We show here that RecQ and RecJ process the nascent DNA at blocked replication forks prior to the resumption of DNA synthesis. The processing involves selective degradation of the nascent lagging DNA strand and it requires both RecQ and RecJ. We suggest that this processing may serve to lengthen the substrate that can be recognized and stabilized by the RecA protein at the replication fork, thereby helping to ensure the accurate recovery of replication after the obstructing lesion has been repaired. Received: 1 June 1999 / Accepted: 28 July 1999