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Olivier Espeli - Regulation of chromosome segregation in bacteria

Speaker : Olivier Espeli - Directeur de Recherche CNRS - Center for Interdisciplinary Research in Biology - Collège de France

When : Wednesday 6th april at 11 am

Where : Salle CO23 (grande salle de réunions du CBP rez-de-chaussée LR6)

Title : Regulation of chromosome segregation in bacteria.

Chromosome segregation is an highly regulated process, work performed in the lab in the recent years revealed that control at various levels of sister chromatid cohesion, which holds together sister chromatids upon replication, is an essential step of the bacterial cell cycle. The process of sister chromosome cohesion is essential for chromosome segregation and DNA repair in eukaryotic cells, it involves a protein complex called cohesins. Although cohesins are absent in bacteria cell biology studies have demonstrated that sister sequences remain co-localized for a period after their replication. We have developed a new genetic recombination assay that probes the ability of newly replicated chromosome loci to interact physically. We show that Sister Chromatid Interaction (SCI) occurs exclusively within a limited time frame after replication. Under regular growth condition, the frequency of sister chromatid interactions is modulated by the activity of Topoisomerase IV, revealing that DNA topology modulates cohesion at the molecular scale in bacteria. Interestingly following genotoxic stress the extent of SCI is increased in an SOS dependent manner revealing a tight connection between cohesion and DNA repair.