46
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: not found

      Pif1 helicase and Polδ promote recombination-coupled DNA synthesis via bubble migration

      research-article

      Read this article at

      ScienceOpenPublisherPMC
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          During DNA repair by homologous recombination (HR), DNA synthesis copies information from a template DNA molecule. Multiple DNA polymerases have been implicated in repair-specific DNA synthesis 1 3 , but it has remained unclear whether a DNA helicase is involved in this reaction. A good candidate is Pif1, an evolutionarily conserved helicase in S. cerevisiae important for break-induced replication (BIR) 4 as well as HR-dependent telomere maintenance in the absence of telomerase 5 found in 10–15% of all cancers 6 . Pif1 plays a role in DNA synthesis across hard-to-replicate sites 7 , 8 and in lagging strand synthesis with Polδ 9 11 . Here we provide evidence that Pif1 stimulates DNA synthesis during BIR and crossover recombination. The initial steps of BIR occur normally in Pif1-deficient cells, but Polδ recruitment and DNA synthesis are decreased, resulting in premature resolution of DNA intermediates into half crossovers. Purified Pif1 protein strongly stimulates Polδ-mediated DNA synthesis from a D-loop made by the Rad51 recombinase. Importantly, Pif1 liberates the newly synthesized strand to prevent the accumulation of topological constraint and to facilitate extensive DNA synthesis via the establishment of a migrating D-loop structure. Our results uncover a novel function of Pif1 and provide insights into the mechanism of HR.

          Related collections

          Most cited references35

          • Record: found
          • Abstract: found
          • Article: not found

          Mechanisms of change in gene copy number.

          Deletions and duplications of chromosomal segments (copy number variants, CNVs) are a major source of variation between individual humans and are an underlying factor in human evolution and in many diseases, including mental illness, developmental disorders and cancer. CNVs form at a faster rate than other types of mutation, and seem to do so by similar mechanisms in bacteria, yeast and humans. Here we review current models of the mechanisms that cause copy number variation. Non-homologous end-joining mechanisms are well known, but recent models focus on perturbation of DNA replication and replication of non-contiguous DNA segments. For example, cellular stress might induce repair of broken replication forks to switch from high-fidelity homologous recombination to non-homologous repair, thus promoting copy number change.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Alternative lengthening of telomeres: models, mechanisms and implications.

            Unlimited cellular proliferation depends on counteracting the telomere attrition that accompanies DNA replication. In human cancers this usually occurs through upregulation of telomerase activity, but in 10-15% of cancers - including some with particularly poor outcome - it is achieved through a mechanism known as alternative lengthening of telomeres (ALT). ALT, which is dependent on homologous recombination, is therefore an important target for cancer therapy. Although dissection of the mechanism or mechanisms of ALT has been challenging, recent advances have led to the identification of several genes that are required for ALT and the elucidation of the biological significance of some phenotypic markers of ALT. This has enabled development of a rapid assay of ALT activity levels and the construction of molecular models of ALT.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              DNA replication through G-quadruplex motifs is promoted by the Saccharomyces cerevisiae Pif1 DNA helicase.

              G-quadruplex (G4) DNA structures are extremely stable four-stranded secondary structures held together by noncanonical G-G base pairs. Genome-wide chromatin immunoprecipitation was used to determine the in vivo binding sites of the multifunctional Saccharomyces cerevisiae Pif1 DNA helicase, a potent unwinder of G4 structures in vitro. G4 motifs were a significant subset of the high-confidence Pif1-binding sites. Replication slowed in the vicinity of these motifs, and they were prone to breakage in Pif1-deficient cells, whereas non-G4 Pif1-binding sites did not show this behavior. Introducing many copies of G4 motifs caused slow growth in replication-stressed Pif1-deficient cells, which was relieved by spontaneous mutations that eliminated their ability to form G4 structures, bind Pif1, slow DNA replication, and stimulate DNA breakage. These data suggest that G4 structures form in vivo and that they are resolved by Pif1 to prevent replication fork stalling and DNA breakage. Copyright © 2011 Elsevier Inc. All rights reserved.
                Bookmark

                Author and article information

                Journal
                0410462
                6011
                Nature
                Nature
                Nature
                0028-0836
                1476-4687
                1 November 2013
                11 September 2013
                17 October 2013
                17 April 2014
                : 502
                : 7471
                : 393-396
                Affiliations
                [1 ]Baylor College of Medicine, Department of Molecular & Human Genetics, One Baylor Plaza, Houston, TX 77030
                [2 ]Department of Molecular Biophysics & Biochemistry, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520
                [3 ]College of Pharmacy, Duksung Women’s University, Seoul 132-714, Korea
                [4 ]Institute of Biochemical Sciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan; Institute of Biological Chemistry, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 115, Taiwan
                [5 ]Department of Biology, School of Science, IUPUI, Indianapolis, Indiana 46202
                [6 ]Department of Biology, College of Liberal Arts and Sciences, University of Iowa, Iowa City, IA 52242-1324
                Author notes
                [# ]correspondence: Grzegorz Ira: gira@ 123456bcm.edu , Patrick Sung: patrick.sung@ 123456yale.edu
                [7]

                These authors contributed equally to this work.

                Present address: Woo-Hyun Chung: College of Pharmacy, Duksung Women’s University, Seoul 132-714, Korea

                Article
                NIHMS518346
                10.1038/nature12585
                3915060
                24025768
                1286a48f-5181-4c6a-ac78-22ef339bcd6b

                Users may view, print, copy, download and text and data- mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use: http://www.nature.com/authors/editorial_policies/license.html#terms

                History
                Funding
                Funded by: National Institute of Environmental Health Sciences : NIEHS
                Award ID: R03 ES016434 || ES
                Funded by: National Institute of General Medical Sciences : NIGMS
                Award ID: R01 GM084242 || GM
                Categories
                Article

                Uncategorized
                Uncategorized

                Comments

                Comment on this article