title: Interplay of DNA supercoiling and catenation during the segregation of sister duplexes.
abstract: The discrete regulation of supercoiling, catenation and knotting by DNA topoisomerases is well documented both in vivo and in vitro, but the interplay between them is still poorly understood. Here we studied DNA catenanes of bacterial plasmids arising as a result of DNA replication in Escherichia coli cells whose topoisomerase IV activity was inhibited. We combined high-resolution two-dimensional agarose gel electrophoresis with numerical simulations in order to better understand the relationship between the negative supercoiling of DNA generated by DNA gyrase and the DNA interlinking resulting from replication of circular DNA molecules. We showed that in those replication intermediates formed in vivo, catenation and negative supercoiling compete with each other. In interlinked molecules with high catenation numbers negative supercoiling is greatly limited. However, when interlinking decreases, as required for the segregation of newly replicated sister duplexes, their negative supercoiling increases. This observation indicates that negative supercoiling plays an active role during progressive decatenation of newly replicated DNA molecules in vivo.
authors: Departamento de Biología Celular y del Desarrollo, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain.
authors: María Luisa
authors: ML
authors: Martínez-Robles
authors: Guillaume
authors: G
authors: Witz
authors: Pablo
authors: P
authors: Hernández
authors: Jorge B
authors: JB
authors: Schvartzman
authors: Andrzej
authors: A
authors: Stasiak
authors: Dora B
authors: DB
authors: Krimer
mesh_terms: D027081:DNA Gyrase / Q000378:metabolism; D004261:DNA Replication; D043864:DNA, Catenated / Q000032:analysis / Q000737:chemistry*; D004278:DNA, Superhelical / Q000032:analysis / Q000737:chemistry*; D015180:Electrophoresis, Gel, Two-Dimensional; D004926:Escherichia coli / Q000235:genetics; D008958:Models, Molecular
chemical_list: D043864:DNA, Catenated; D004278:DNA, Superhelical; D027081:DNA Gyrase