Nucleic Acids Research Advance Access originally published online on June 24, 2009
Nucleic Acids Research 2009 37(15):5126-5137; doi:10.1093/nar/gkp530
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Nucleic Acids Research, 2009, Vol. 37, No. 15 5126-5137
© 2009 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Structural Biology |
Interplay of DNA supercoiling and catenation during the segregation of sister duplexes
1Departamento de Biología Celular y del Desarrollo, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain, 2Centre Intégratif de Génomique, Faculté de Biologie et de Médecine, Université de Lausanne, 1015 Lausanne and 3Laboratoire de Physique de la Matière Vivante, Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
*To whom correspondence should be addressed. Tel: +34 91 837 3112 ext. 4232; Fax: +34 91 536 0432; Email: schvartzman{at}cib.csic.es
Correspondence may also be addressed to Andrzej Stasiak. Tel: +41 21 692 4282; Fax: +41 21 692 4105; Email: andrzej.stasiak{at}unil.ch
Received May 8, 2009. Revised June 4, 2009. Accepted June 5, 2009.
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.