title: Undesigned selection for replication termination of bacterial chromosomes.
abstract: The oriC DNA replication origin in bacterial chromosomes, the location of which appears to be physically identified, is genetically regulated by relevant molecular machinery. In contrast, the location of the terminus remains obscure for many bacterial replicons, except for terC, the proposed and well-studied chromosome termination site in certain bacteria. The terC locus, which is composed of specific sequences for its binding protein, is located at a site opposite from oriC, exhibiting a symmetric structure around the oriC-terC axis. Here, we investigated Bacillus subtilis 168 strains whose axes were hindered and found that the native terC function was robust. However, eradication of terminus region specific binding protein resulted in the natural terC sites not being used for termination; instead, new termini were selected at a location exactly opposite to oriC. We concluded that replication generally terminates at the loci where the two approaching replisomes meet. This site was automatically selected, and two replisomes moving at the same rate supported symmetrical chromosome structures relative to oriC. The rule, which was even validated by artificial chromosomes irrespective of oriC, should be general for replicons administered by two replisomes.
authors.affiliation: Institute for Advanced Biosciences, Keio University, Yamagata 997-0017, Japan. Electronic address: ciconia@sfc.keio.ac.jp.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Kono
authors.affiliation: Institute for Advanced Biosciences, Keio University, Yamagata 997-0017, Japan.
authors.forename: Kazuharu
authors.initials: K
authors.lastname: Arakawa
authors.affiliation: Institute for Advanced Biosciences, Keio University, Yamagata 997-0017, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Sato
authors.affiliation: Department of Bioscience, Tokyo University of Agriculture, Tokyo 156-8502, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yoshikawa
authors.affiliation: Institute for Advanced Biosciences, Keio University, Yamagata 997-0017, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Tomita
authors.affiliation: Institute for Advanced Biosciences, Keio University, Yamagata 997-0017, Japan. Electronic address: mita2001@sfc.keio.ac.jp.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Itaya
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000235:genetics*; D004261:DNA Replication / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation / Q000235:genetics; D051738:Origin Recognition Complex / Q000235:genetics*; D012641:Selection, Genetic; D013728:Terminator Regions, Genetic / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C114650:OriC chromosomal replication origin; D051738:Origin Recognition Complex
keywords: Bacillus subtilis; circular chromosome; genomic structure; high-throughput sequencing; replication terminus