title: Visualization of recombination-mediated damage bypass by template switching.
abstract: Template switching (TS) mediates damage bypass via a recombination-related mechanism involving PCNA polyubiquitination and polymerase δ-dependent DNA synthesis. Using two-dimensional gel electrophoresis and EM, here we characterize TS intermediates arising in Saccharomyces cerevisiae at a defined chromosome locus, identifying five major families of intermediates. Single-stranded DNA gaps of 150-200 nt, and not DNA ends, initiate TS by strand invasion. This causes reannealing of the parental strands and exposure of the nondamaged newly synthesized chromatid, which serves as a replication template for the other blocked nascent strand. Structures resembling double Holliday junctions, postulated to be central double-strand break-repair intermediates but so far visualized only in meiosis, mediate late stages of TS before being processed to hemicatenanes. Our results reveal the DNA transitions accounting for recombination-mediated DNA-damage tolerance in mitotic cells and replication under conditions of genotoxic stress.
authors.affiliation: 1] Istituto Fondazione Italiana per la Ricerca sul Cancro (FIRC) di Oncologia Molecolare (IFOM), Milan, Italy. [2] Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Giannattasio
authors.affiliation: Institute of Molecular Cancer Research, University of Zürich, Zürich, Switzerland.
authors.forename: Katharina
authors.initials: K
authors.lastname: Zwicky
authors.affiliation: 1] Institute of Molecular Cancer Research, University of Zürich, Zürich, Switzerland. [2].
authors.forename: Cindy
authors.initials: C
authors.lastname: Follonier
authors.affiliation: 1] Istituto Fondazione Italiana per la Ricerca sul Cancro (FIRC) di Oncologia Molecolare (IFOM), Milan, Italy. [2] Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Foiani
authors.affiliation: Institute of Molecular Cancer Research, University of Zürich, Zürich, Switzerland.
authors.forename: Massimo
authors.initials: M
authors.lastname: Lopes
authors.affiliation: Istituto Fondazione Italiana per la Ricerca sul Cancro (FIRC) di Oncologia Molecolare (IFOM), Milan, Italy.
authors.forename: Dana
authors.initials: D
authors.lastname: Branzei
mesh_terms: D002842:Chromatids; D004249:DNA Damage; D004258:DNA Polymerase III / Q000235:genetics; D004260:DNA Repair; D004261:DNA Replication / Q000235:genetics*; D045566:DNA, Cruciform; D004271:DNA, Fungal / Q000096:biosynthesis / Q000235:genetics; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D013698:Templates, Genetic; D054875:Ubiquitination
chemical_list: D045566:DNA, Cruciform; D004271:DNA, Fungal; D018809:Proliferating Cell Nuclear Antigen; D029701:Saccharomyces cerevisiae Proteins; D004258:DNA Polymerase III