title: Nucleoid organization in the radioresistant bacterium Deinococcus radiodurans.
abstract: Processes favoring the exceptional resistance to genotoxic stress of Deinococcus radiodurans are not yet completely characterized. It was postulated that its nucleoid and chromosome(s) organization could participate in the DNA double strand break repair process. Here, we investigated the organization of chromosome 1 by localization of three chromosomal loci including oriC, Ter and a locus located in its left arm. For this purpose, we used a ParB-parS system to visualize the position of the loci before and after exposure to γ-rays. By comparing the number of fluorescent foci with the number of copies of the studied loci present in the cells measured by quantitative polymerase chain reaction (qPCR), we demonstrated that the 4-10 copies of chromosome 1 per cell are dispersed within the nucleoid before irradiation, indicating that the chromosome copies are not prealigned. Chromosome segregation is progressive but not co-ordinated, allowing each locus to be paired with its sister during part of the cell cycle. After irradiation, the nucleoid organization is modified, involving a transient alignment of the loci in the late stage of DNA repair and a delay of segregation of the Ter locus. We discuss how these events can influence DNA double strand break repair.
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris Sud, Bâtiment 409, Orsay, 91405, France.
authors.forename: Fanny Marie
authors.initials: FM
authors.lastname: Passot
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris Sud, Bâtiment 409, Orsay, 91405, France.
authors.forename: Hong Ha
authors.initials: HH
authors.lastname: Nguyen
authors.affiliation: Plateforme Intégrée IMAGIF - CNRS, Avenue de la Terrasse, Gif sur Yvette, 91198, France.
authors.forename: Cloelia
authors.initials: C
authors.lastname: Dard-Dascot
authors.affiliation: Plateforme Intégrée IMAGIF - CNRS, Avenue de la Terrasse, Gif sur Yvette, 91198, France.
authors.forename: Claude
authors.initials: C
authors.lastname: Thermes
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris Sud, Bâtiment 409, Orsay, 91405, France.
authors.forename: Pascale
authors.initials: P
authors.lastname: Servant
authors.affiliation: Center for Interdisciplinary Research In Biology (CIRB), Collège de France, CNRS UMR 7241, INSERM U1050, 11 place Marcelin Berthelot, Paris, 75005, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Espéli
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris Sud, Bâtiment 409, Orsay, 91405, France.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Sommer
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D042002:Chromatin Assembly and Disassembly; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage / Q000528:radiation effects; D004260:DNA Repair; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D034301:Deinococcus / Q000166:cytology / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects*; D011836:Radiation Tolerance / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C040330:histone-like protein HU, bacteria