42
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      Evidence for Two Different Regulatory Mechanisms Linking Replication and Segregation of Vibrio cholerae Chromosome II

      research-article

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Understanding the mechanisms that coordinate replication initiation with subsequent segregation of chromosomes is an important biological problem. Here we report two replication-control mechanisms mediated by a chromosome segregation protein, ParB2, encoded by chromosome II of the model multichromosome bacterium, Vibrio cholerae. We find by the ChIP-chip assay that ParB2, a centromere binding protein, spreads beyond the centromere and covers a replication inhibitory site (a 39-mer). Unexpectedly, without nucleation at the centromere, ParB2 could also bind directly to a related 39-mer. The 39-mers are the strongest inhibitors of chromosome II replication and they mediate inhibition by binding the replication initiator protein. ParB2 thus appears to promote replication by out-competing initiator binding to the 39-mers using two mechanisms: spreading into one and direct binding to the other. We suggest that both these are novel mechanisms to coordinate replication initiation with segregation of chromosomes.

          Author Summary

          Replication and segregation are the two main processes that maintain chromosomes in growing cells. In eukaryotes, the two processes are restricted to distinct phases of the cell cycle. In bacteria, segregation follows replication initiation with a modest lag. Influences of one process on the other have been postulated. The act of replication has been suggested to provide a motive force in chromosome segregation. Moreover, segregation proteins (ParA) have been found to interact with and control the replication initiator, DnaA. Here we show that in V. cholerae chromosome II, which is believed to have originated from a plasmid, a centromere binding protein (ParB) could control replication by two distinct mechanisms: spreading from a centromeric site into the replication-control region, and direct binding to the primary replication-control site, which has limited homology to the centromeric site. These studies establish that Par proteins can influence replication by at least three mechanisms. Homologous Par proteins participate in plasmid segregation but they are not known to influence plasmid replication. The expanded role of Par proteins appears likely to have been warranted to coordinate chromosomal replication and segregation with the cell cycle, which appears less of an issue in plasmid maintenance.

          Related collections

          Most cited references52

          • Record: found
          • Abstract: found
          • Article: not found

          Comprehensive analysis of heterochromatin- and RNAi-mediated epigenetic control of the fission yeast genome.

          The organization of eukaryotic genomes into distinct structural and functional domains is important for the regulation and transduction of genetic information. Here, we investigated heterochromatin and euchromatin profiles of the entire fission yeast genome and explored the role of RNA interference (RNAi) in genome organization. Histone H3 methylated at Lys4, which defines euchromatin, was not only distributed across most of the chromosomal landscape but was also present at the centromere core, the site of kinetochore assembly. In contrast, histone H3 methylated at Lys9 and its interacting protein Swi6/HP1, which define heterochromatin, coated extended domains associated with a variety of repeat elements and small islands corresponding to meiotic genes. Notably, RNAi components were distributed throughout all these heterochromatin domains, and their localization depended on Clr4/Suv39h histone methyltransferase. Sequencing of small interfering RNAs (siRNAs) associated with the RITS RNAi effector complex identified hot spots of siRNAs, which mapped to a diverse array of elements in these RNAi-heterochromatin domains. We found that Clr4/Suv39h predominantly silenced repeat elements whose derived transcripts, transcribed mainly by RNA polymerase II, serve as a source for siRNAs. Our analyses also uncover an important role for the RNAi machinery in maintaining genomic integrity.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Recruitment of condensin to replication origin regions by ParB/SpoOJ promotes chromosome segregation in B. subtilis.

            Proper segregation of DNA replication products is essential in all cells. In Bacillus subtilis, two protein complexes have been implicated in this process: the ParAB homologs, Soj and Spo0J, and the bacterial Smc/ScpAB complex, also called condensin. Here we demonstrate that Smc is highly enriched in the region around the origin of replication, specifically near parS sites to which Spo0J binds and at highly transcribed genes. Furthermore, we find that efficient recruitment of Smc to a large region around the origin of replication depends on the presence of Spo0J. We show that Spo0J performs two independent functions: regulation of initiation of DNA replication via Soj and promotion of chromosome segregation by Smc recruitment. Our results demonstrate a direct functional interaction between two widely conserved systems involved in chromosome replication and segregation.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Pushing and pulling in prokaryotic DNA segregation.

              In prokaryotes, DNA can be segregated by three different types of cytoskeletal filaments. The best-understood type of partitioning (par) locus encodes an actin homolog called ParM, which forms dynamically unstable filaments that push plasmids apart in a process reminiscent of mitosis. However, the most common type of par locus, which is present on many plasmids and most bacterial chromosomes, encodes a P loop ATPase (ParA) that distributes plasmids equidistant from one another on the bacterial nucleoid. A third type of par locus encodes a tubulin homolog (TubZ) that forms cytoskeletal filaments that move rapidly with treadmill dynamics. Copyright 2010 Elsevier Inc. All rights reserved.
                Bookmark

                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS Genet
                PLoS Genet
                plos
                plosgen
                PLoS Genetics
                Public Library of Science (San Francisco, USA )
                1553-7390
                1553-7404
                June 2013
                June 2013
                20 June 2013
                : 9
                : 6
                : e1003579
                Affiliations
                [1 ]Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
                [2 ]Genome Analysis Unit, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
                [3 ]Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
                Institute of Molecular and Cell Biology (IMCB), A*STAR, Singapore
                Author notes

                The authors have declared that no competing interests exist.

                Conceived and designed the experiments: TVC JHB PCF MB DKC. Performed the experiments: TVC JHB MB DKC. Analyzed the data: TVC JHB PCF MB DKC. Contributed reagents/materials/analysis tools: TVC JHB PCF MB DKC. Wrote the paper: TVC JHB PCF MB DKC.

                [¤]

                Current address: Department of Internal Medicine, Medical Research Building, University of Texas Medical Branch (UTMB), Galveston, Texas, United States of America.

                Article
                PGENETICS-D-12-02653
                10.1371/journal.pgen.1003579
                3688505
                23818869
                384325df-c49e-4da7-abcb-a467bde39397
                Copyright @ 2013

                This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

                History
                : 24 October 2012
                : 6 May 2013
                Page count
                Pages: 12
                Funding
                This work was supported by the Intramural Research Program of the Center for Cancer Research, NCI, NIH, and funding from the Swiss National Science Foundation (grant 31003A_127029 to MB). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Categories
                Research Article
                Biology

                Genetics
                Genetics

                Comments

                Comment on this article