RESUMEN
Catenation links between sister chromatids are formed progressively during DNA replication and are involved in the establishment of sister chromatid cohesion. Topo IV is a bacterial type II topoisomerase involved in the removal of catenation links both behind replication forks and after replication during the final separation of sister chromosomes. We have investigated the global DNA-binding and catalytic activity of Topo IV in E. coli using genomic and molecular biology approaches. ChIP-seq revealed that Topo IV interaction with the E. coli chromosome is controlled by DNA replication. During replication, Topo IV has access to most of the genome but only selects a few hundred specific sites for its activity. Local chromatin and gene expression context influence site selection. Moreover strong DNA-binding and catalytic activities are found at the chromosome dimer resolution site, dif, located opposite the origin of replication. We reveal a physical and functional interaction between Topo IV and the XerCD recombinases acting at the dif site. This interaction is modulated by MatP, a protein involved in the organization of the Ter macrodomain. These results show that Topo IV, XerCD/dif and MatP are part of a network dedicated to the final step of chromosome management during the cell cycle.
Asunto(s)
Proteínas Cromosómicas no Histona/genética , Replicación del ADN/genética , Topoisomerasa de ADN IV/genética , Proteínas de Escherichia coli/genética , Integrasas/genética , Sitios de Unión/genética , Dominio Catalítico/genética , Ciclo Celular/genética , División Celular/genética , Cromátides/genética , Proteínas Cromosómicas no Histona/metabolismo , Segregación Cromosómica/genética , Cromosomas Bacterianos/genética , Topoisomerasa de ADN IV/metabolismo , Escherichia coli/enzimología , Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Integrasas/metabolismo , Intercambio de Cromátides Hermanas/genéticaRESUMEN
Bacteria face the problem of segregating their gigantic chromosomes without a segregation period restricted in time and space, as Eukaryotes do. Segregation thus involves multiple activities, general or specific of a chromosome region and differentially controlled. Recent advances show that these various mechanisms conform to a "pair and release" rule, which appears as a general rule in DNA segregation. We describe the latest advances in segregation of bacterial chromosomes with emphasis on the different pair and release mechanisms.