Etude des liens entre la cohésion des chromatides soeurs et réparation de l'ADN

par Adrien Camus

Projet de thèse en Infectiologie

Sous la direction de Olivier Espeli.

Thèses en préparation à l'Université Paris sciences et lettres , dans le cadre de École doctorale Bio Sorbonne Paris Cité , en partenariat avec Centre Interdisciplinaire de Recherche en Biologie (laboratoire) et de Collège de France (établissement opérateur d'inscription) depuis le 01-11-2018 .


  • Résumé

    All cells must accurately copy and maintain their DNA to ensure the faithful transmission of their genetic material to the next generation. DNA replication aggravates preexisting DNA damage, which then blocks subsequent replication. Mutants with malfunctioning replisomes or with elevated levels of DNA damage depend on homologous recombination (HR) to survive. Repair of DNA double strand breaks (DSBs), single-stranded gaps (SSGs) and DNA adducts such as interstrand crosslinks (ICL) involves HR pathways (Kuzminov, 1999). HR also drives genetic exchanges and genome dynamics. HR permits the use of homologous sequences for repair, but how homology search, the exploration of the genome for homologous DNA sequences, is conducted in a crowded nucleus or bacterial nucleoid remains poorly understood. At first glance, homology search appears to be simplified for DSB repair after replication as the homologous sequence is seemingly in close reach. Homologous sister chromatids are tied together by cohesin rings in Eukaryotes (Nasmyth & Haering, 2009) and topological linking, in both Eukaryotes and Bacteria (Lesterlin et al, 2012; Mariezcurrena & Uhlmann, 2017). Topological links maintain contacts between sister chromatids, however, our recent work revealed that these links are not used by wild type cells to support HR. We have recently demonstrated that in E. coli the main pathway of repair of ICLs and replicative DSBs involves an SOS induced protein, RecN (Vickridge et al, 2017). RecN induction halts sister chromatid segregation and eventually provokes the re-alignment of recently segregated loci. These events enhance the repair of broken sister chromatids. These characteristics, the strong conservation of recN in bacteria and its resemblance with SMC proteins such as cohesins make the characterization of its mode of action, the role of its partners and its impact on the outcome of DNA repair particularly exciting. The main goal of the PhD project is to unravel the molecular mechanisms used by RecN to promote (directly or indirectly) sister chromatid cohesion. First the PhD candidate will analyze the loading and dynamics of RecN on sister chromatids with ChIP- seq and live super-resolution microscopy approaches. Second we will benefit from a collaboration with the FX Barre's team in Gif sur Yvette to analyze, with a recently developed method, the cohesion at the genome wide level in different genetic and environmental contexts.

  • Titre traduit

    Study of the links between sister chromatid cohesion and DNA repair


  • Résumé

    All cells must accurately copy and maintain their DNA to ensure the faithful transmission of their genetic material to the next generation. DNA replication aggravates preexisting DNA damage, which then blocks subsequent replication. Mutants with malfunctioning replisomes or with elevated levels of DNA damage depend on homologous recombination (HR) to survive. Repair of DNA double strand breaks (DSBs), single-stranded gaps (SSGs) and DNA adducts such as interstrand crosslinks (ICL) involves HR pathways (Kuzminov, 1999). HR also drives genetic exchanges and genome dynamics. HR permits the use of homologous sequences for repair, but how homology search, the exploration of the genome for homologous DNA sequences, is conducted in a crowded nucleus or bacterial nucleoid remains poorly understood. At first glance, homology search appears to be simplified for DSB repair after replication as the homologous sequence is seemingly in close reach. Homologous sister chromatids are tied together by cohesin rings in Eukaryotes (Nasmyth & Haering, 2009) and topological linking, in both Eukaryotes and Bacteria (Lesterlin et al, 2012; Mariezcurrena & Uhlmann, 2017). Topological links maintain contacts between sister chromatids, however, our recent work revealed that these links are not used by wild type cells to support HR. We have recently demonstrated that in E. coli the main pathway of repair of ICLs and replicative DSBs involves an SOS induced protein, RecN (Vickridge et al, 2017). RecN induction halts sister chromatid segregation and eventually provokes the re-alignment of recently segregated loci. These events enhance the repair of broken sister chromatids. These characteristics, the strong conservation of recN in bacteria and its resemblance with SMC proteins such as cohesins make the characterization of its mode of action, the role of its partners and its impact on the outcome of DNA repair particularly exciting. The main goal of the PhD project is to unravel the molecular mechanisms used by RecN to promote (directly or indirectly) sister chromatid cohesion. First the PhD candidate will analyze the loading and dynamics of RecN on sister chromatids with ChIP- seq and live super-resolution microscopy approaches. Second we will benefit from a collaboration with the FX Barre's team in Gif sur Yvette to analyze, with a recently developed method, the cohesion at the genome wide level in different genetic and environmental contexts.