title: Pif1 helicase and Polδ promote recombination-coupled DNA synthesis via bubble migration.
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, but it has remained unclear whether a DNA helicase is involved in this reaction. A good candidate DNA helicase is Pif1, an evolutionarily conserved helicase in Saccharomyces cerevisiae important for break-induced replication (BIR) as well as HR-dependent telomere maintenance in the absence of telomerase found in 10-15% of all cancers. Pif1 has a role in DNA synthesis across hard-to-replicate sites and in lagging-strand synthesis with polymerase δ (Polδ). 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. Notably, 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.
authors.affiliation: Baylor College of Medicine, Department of Molecular & Human Genetics, One Baylor Plaza, Houston, Texas 77030, USA.
authors.forename: Marenda A
authors.initials: MA
authors.lastname: Wilson
authors.forename: YoungHo
authors.initials: Y
authors.lastname: Kwon
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Xu
authors.forename: Woo-Hyun
authors.initials: WH
authors.lastname: Chung
authors.forename: Peter
authors.initials: P
authors.lastname: Chi
authors.forename: Hengyao
authors.initials: H
authors.lastname: Niu
authors.forename: Ryan
authors.initials: R
authors.lastname: Mayle
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Chen
authors.forename: Anna
authors.initials: A
authors.lastname: Malkova
authors.forename: Patrick
authors.initials: P
authors.lastname: Sung
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Ira
mesh_terms: D003434:Crossing Over, Genetic; D004265:DNA Helicases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004258:DNA Polymerase III / Q000378:metabolism*; D004260:DNA Repair; D004261:DNA Replication; D004271:DNA, Fungal / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D009690:Nucleic Acid Conformation; D051135:Rad51 Recombinase / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004271:DNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; C495151:RAD51 protein, S cerevisiae; D051135:Rad51 Recombinase; D004258:DNA Polymerase III; C085463:PIF1 protein, S cerevisiae; D004265:DNA Helicases
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