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Polymerase δ replicates both strands after homologous recombination–dependent fork restart


To maintain genetic stability, DNA must be replicated only once per cell cycle, and replication must be completed even when individual replication forks are inactivated. Because fork inactivation is common, passive convergence of an adjacent fork is insufficient to rescue all inactive forks. Thus, eukaryotic cells have evolved homologous recombination–dependent mechanisms to restart persistent inactive forks. Completing DNA synthesis via homologous recombination–restarted replication (HoRReR) ensures cell survival, but at a cost. One such cost is increased mutagenesis because HoRReR is more error prone than canonical replication. This increased error rate implies the HoRReR mechanism is distinct from that of a canonical fork. Here we demonstrate, in Schizosaccharomyces pombe, that a DNA sequence duplicated by HoRReR during S phase is replicated semiconservatively, but both the leading and lagging strands are synthesized by DNA polymerase δ.

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Figure 1: Polδ, but not Polɛ, participates in bulk DNA synthesis after HR restart.
Figure 2: Polδ usage is relatively uniform, and Polα usage decreases.
Figure 3: HR-restarted replication is semiconservative.
Figure 4: Instability resulting from HR-restarted replication is not intrinsic to leading-strand synthesis by Polδ.
Figure 5: Polδ usage correlates with fragile sites.


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This work was supported by Project Z01 ES065070 (T.A.K.) from the Division of Intramural Research of the US National Institutes of Health, by Medical Research Council (UK) grants G0801078 and G1100074 (A.M.C.) and by European Research Council grant 268788-SMI-DDR (A.M.C.). We thank H. Masukata (Osaka University) for the cdc20::hphMX6-Pnmt1-cdc20CTD strain.

Author information




A.M.C. conceived the study. A.M.C., T.A.K., I.M. and J.M.M. designed the experimental approach. I.M., K'I.M., S.M., Y.D., A.K. and M.S. performed experiments and interpreted data. I.M. and A.M.C. wrote the manuscript. T.A.K. and J.M.M. edited the manuscript.

Corresponding author

Correspondence to Antony M Carr.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Data Set 1

Full autoradiographs of all blots used in the figures (PDF 13572 kb)

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Miyabe, I., Mizuno, K., Keszthelyi, A. et al. Polymerase δ replicates both strands after homologous recombination–dependent fork restart. Nat Struct Mol Biol 22, 932–938 (2015).

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