Dynamique des chromosomes / Chromosome dynamics

Recherche Page web : https://www.college-de-france.fr/site/en-cirb/espeli.htm. Publications El Sayyed H. et Espéli O., « Mapping E. coli Topoisomerase IV binding and activity sites », Methods in Molecular Biology, vol. 1703, 2018, p. 87-94, DOI : 10.1007/978-1-4939-7459-7_6. Leh H., Khodr A., Bouger M.-C., Sclavi B., Rimsky S. et Bury-Moné S., « Bacterial-chromatin structural proteins regulate the bimodal expression of the locus of enterocyte effacement (LEE) pathogenicity island in enteropat..

Chromosome Structuring Limits Genome Plasticity in Escherichia coli

Chromosome organizations of related bacterial genera are well conserved despite a very long divergence period. We have assessed the forces limiting bacterial genome plasticity in Escherichia coli by measuring the respective effect of altering different parameters, including DNA replication, compositional skew of replichores, coordination of gene expression with DNA replication, replication-associated gene dosage, and chromosome organization into macrodomains. Chromosomes were rearranged by large inversions. Changes in the compositional skew of replichores, in the coordination of gene expression with DNA replication or in the replication-associated gene dosage have only a moderate effect on cell physiology because large rearrangements inverting the orientation of several hundred genes inside a replichore are only slightly detrimental. By contrast, changing the balance between the two replication arms has a more drastic effect, and the recombinational rescue of replication forks is required for cell viability when one of the chromosome arms is less than half than the other one. Macrodomain organization also appears to be a major factor restricting chromosome plasticity, and two types of inverted configurations severely affect the cell cycle. First, the disruption of the Ter macrodomain with replication forks merging far from the normal replichore junction provoked chromosome segregation defects. The second major problematic configurations resulted from inversions between Ori and Right macrodomains, which perturb nucleoid distribution and early steps of cytokinesis. Consequences for the control of the bacterial cell cycle and for the evolution of bacterial chromosome configuration are discussed

The MatP/matS Site-Specific System Organizes the Terminus Region of the E. coli Chromosome into a Macrodomain

The organization of the Escherichia coli chromosome into insulated macrodomains influences the segregation of sister chromatids and the mobility of chromosomal DNA. Here, we report that organization of the Terminus region (Ter) into a macrodomain relies on the presence of a 13 bp motif called matS repeated 23 times in the 800-kb-long domain. matS sites are the main targets in the E. coli chromosome of a newly identified protein designated MatP. MatP accumulates in the cell as a discrete focus that colocalizes with the Ter macrodomain. The effects of MatP inactivation reveal its role as main organizer of the Ter macrodomain: in the absence of MatP, DNA is less compacted, the mobility of markers is increased, and segregation of Ter macrodomain occurs early in the cell cycle. Our results indicate that a specific organizational system is required in the Terminus region for bacterial chromosome management during the cell cycle

Long-Range Chromosome Organization in E. coli: A Site-Specific System Isolates the Ter Macrodomain

The organization of the Escherichia coli chromosome into a ring composed of four macrodomains and two less-structured regions influences the segregation of sister chromatids and the mobility of chromosomal DNA. The structuring of the terminus region (Ter) into a macrodomain relies on the interaction of the protein MatP with a 13-bp target called matS repeated 23 times in the 800-kb-long domain. Here, by using a new method that allows the transposition of any chromosomal segment at a defined position on the genetic map, we reveal a site-specific system that restricts to the Ter region a constraining process that reduces DNA mobility and delays loci segregation. Remarkably, the constraining process is regulated during the cell cycle and occurs only when the Ter MD is associated with the division machinery at mid-cell. The change of DNA properties does not rely on the presence of a trans-acting mechanism but rather involves a cis-effect acting at a long distance from the Ter region. Two specific 12-bp sequences located in the flanking Left and Right macrodomains and a newly identified protein designated YfbV conserved with MatP through evolution are required to impede the spreading of the constraining process to the rest of the chromosome. Our results unravel a site-specific system required to restrict to the Ter region the consequences of anchoring the Ter MD to the division machinery

Dynamique des chromosomes

    Responsable : Olivier Espéli Our laboratory is interested in the analysis of the dynamics chromosome conformation in response to stimuli or stresses coming from the cytoplasm or the environment. We use a combination of genetic, genomic and cell biology tools to monitor chromosome conformation and movements. Publications Passot F.M., Nguyen H.H., Dard-Dascot C., Thermes C., Servant P., Espéli O. et Sommer S., « Nucleoid organization in the radioresistant bacterium Deinococcus radiodurans »..

Dynamique des chromosomes

    Responsable : Olivier Espéli Recherche Notre laboratoire s’intéresse à l’analyse de l’évolution de la structure et de l’expression des chromosomes en réponse à des stimuli ou des stress dont l’origine est le cytoplasme ou l’environnement. Nous utilisons une combinaison de méthodes de génétique, génomique et biologie cellulaire pour décrire ces changements de conformations des chromosomes et leurs mouvements. Notre modèle d’étude principal est la bactérie Escherichia coli. Nous développons..

Dynamique des chromosomes / Chromosome dynamics

    Responsable : Olivier Espéli Recherche Bacteria are highly organized cells that can multiply rapidly when the environment is favorable. To reach a fast growth rate bacteria rely on a strongly regulated cell cycle that coordinate the genome replication, chromosome segregation, cell elongation and division. However when the environment is less favorable the bacteria adapts their growing regime to protect themselves. The lack of nutrients or the presence of stress (reactive oxygen species, a..

Dynamique des chromosomes / Chromosome dynamics

    Responsable : Olivier Espéli Recherche : Cell cycle and chromosome dynamics Bacteria are highly organized cells that can multiply rapidly when the environment is favorable. To reach a fast growth rate bacteria rely on a strongly regulated cell cycle that coordinate the genome replication, chromosome segregation, cell elongation and division. However when the environment is less favorable the bacteria adapts their growing regime to protect themselves. The lack of nutrients or the presence ..

Organization of the Escherichia coli chromosome into macrodomains and its possible functional implications.

Recent advances in fluorescent microscopy have revealed the non-random organization of chromosomes in bacterial cells. In Escherichia coli, segments included in two large regions show similar localization patterns allowing the definition of two macrodomains centered, respectively, on the centromere-like site migS (the Ori domain) and the replication terminus (the Ter domain). A genetic system measuring long distance DNA interactions confirmed the macrodomain organization of the chromosome and revealed the existence of two additional macrodomains flanking the Ter domain. Altogether, the E. coli chromosome appears to have an open ring-like conformation. Recent developments regarding various stages of chromosome biology such as replication, sister chromatid cohesion, segregation, and chromosome choreography, have considerably improved our understanding of the coordination of chromosome dynamics with the cell cycle. The possible involvement of macrodomains in these various processes is discussed