A Fork Trap in the Chromosomal Termination Area Is Highly Conserved across All Phylogenetic Groups.

Termination of DNA replication, the final stage of genome duplication, is surprisingly complex, and failures to bring DNA synthesis to an accurate conclusion can impact genome stability and cell viability. In , termination takes place in a specialised termination area opposite the origin. A 'replication fork trap' is formed by unidirectional fork barriers via the binding of Tus protein to genomic sites. Such a fork trap system is found in some bacterial species, but it appears not to be a general feature of bacterial chromosomes. The biochemical properties of fork trap systems have been extensively characterised, but little is known about their precise physiological roles. In this study, we compare locations and distributions of terminator sites in genomes across all phylogenetic groups, including . Our analysis shows that all sites are highly conserved in , with slightly more variability in the genomes. Our sequence analysis of sites and Tus proteins shows that the fork trap is likely to be active in all strains investigated. In addition, our analysis shows that the chromosome dimer resolution site is consistently located between the innermost sites, even if rearrangements have changed the location of the innermost termination area. Our data further support the idea that the replication fork trap has an important physiological role that provides an evolutionary advantage.