title: UV stalled replication forks restart by re-priming in human fibroblasts.
abstract: Restarting stalled replication forks is vital to avoid fatal replication errors. Previously, it was demonstrated that hydroxyurea-stalled replication forks rescue replication either by an active restart mechanism or by new origin firing. To our surprise, using the DNA fibre assay, we only detect a slightly reduced fork speed on a UV-damaged template during the first hour after UV exposure, and no evidence for persistent replication fork arrest. Interestingly, no evidence for persistent UV-induced fork stalling was observed even in translesion synthesis defective, Polη(mut) cells. In contrast, using an assay to measure DNA molecule elongation at the fork, we observe that continuous DNA elongation is severely blocked by UV irradiation, particularly in UV-damaged Polη(mut) cells. In conclusion, our data suggest that UV-blocked replication forks restart effectively through re-priming past the lesion, leaving only a small gap opposite the lesion. This allows continuation of replication on damaged DNA. If left unfilled, the gaps may collapse into DNA double-strand breaks that are repaired by a recombination pathway, similar to the fate of replication forks collapsed after hydroxyurea treatment.
authors.affiliation: Department of Genetics, Microbiology and Toxicology, Stockholm University, S-10691 Stockholm, Sweden.
authors.forename: Ingegerd
authors.initials: I
authors.lastname: Elvers
authors.forename: Fredrik
authors.initials: F
authors.lastname: Johansson
authors.forename: Petra
authors.initials: P
authors.lastname: Groth
authors.forename: Klaus
authors.initials: K
authors.lastname: Erixon
authors.forename: Thomas
authors.initials: T
authors.lastname: Helleday
mesh_terms: D002460:Cell Line; D004247:DNA / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000032:analysis; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D013698:Templates, Genetic; D014466:Ultraviolet Rays
chemical_list: D004277:DNA, Single-Stranded; D004247:DNA