title: Continued primer synthesis at stalled replication forks contributes to checkpoint activation.
abstract: Stalled replication forks activate and are stabilized by the ATR (ataxia-telangiectasia mutated and Rad3 related)-mediated checkpoint, but ultimately, they must also recover from the arrest. Although primed single-stranded DNA (ssDNA) is sufficient for checkpoint activation, it is still unknown how this signal is generated at a stalled replication fork. Furthermore, it is not clear how recovery and fork restart occur in higher eukaryotes. Using Xenopus laevis egg extracts, we show that DNA replication continues at a stalled fork through the synthesis and elongation of new primers independent of the checkpoint. This synthesis is dependent on the activity of proliferating cell nuclear antigen, Pol-delta, and Pol-epsilon, and it contributes to the phosphorylation of Chk1. We also used defined DNA structures to show that for a fixed amount of ssDNA, increasing the number of primer-template junctions strongly enhances Chk1 phosphorylation. These results suggest that new primers are synthesized at stalled replication forks by the leading and lagging strand polymerases and that accumulation of these primers may contribute to checkpoint activation.
authors.affiliation: Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Van
authors.forename: Shan
authors.initials: S
authors.lastname: Yan
authors.forename: W Matthew
authors.initials: WM
authors.lastname: Michael
authors.forename: Shou
authors.initials: S
authors.lastname: Waga
authors.forename: Karlene A
authors.initials: KA
authors.lastname: Cimprich
mesh_terms: D000818:Animals; D016590:Aphidicolin / Q000378:metabolism; D064007:Ataxia Telangiectasia Mutated Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D000071877:Checkpoint Kinase 1; D002843:Chromatin / Q000378:metabolism; D004256:DNA Polymerase I / Q000235:genetics / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors / Q000378:metabolism; D005260:Female; D008297:Male; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000235:genetics / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002843:Chromatin; D017931:DNA Primers; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C509993:TopBP1 protein, Xenopus; D029867:Xenopus Proteins; D016590:Aphidicolin; D011494:Protein Kinases; C576898:Atr protein, Xenopus; D064007:Ataxia Telangiectasia Mutated Proteins; D000071877:Checkpoint Kinase 1; C000605875:Chek1 protein, Xenopus; D017346:Protein Serine-Threonine Kinases; D004256:DNA Polymerase I
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