title: Linear plasmids mobilize linear but not circular chromosomes in Streptomyces: support for the 'end first' model of conjugal transfer.
abstract: Gram-positive bacteria of the genus Streptomyces possess linear chromosomes and linear plasmids capped by terminal proteins covalently bound to the 5' ends of the DNA. The linearity of Streptomyces chromosomes raises the question of how they are transferred during conjugation, particularly when the mobilizing plasmids are also linear. The classical rolling circle replication model for transfer of circular plasmids and chromosomes from an internal origin cannot be applied to this situation. Instead it has been proposed that linear Streptomyces plasmids mobilize themselves and the linear chromosomes from their telomeres using terminal-protein-primed DNA synthesis. In support of this 'end first' model, we found that artificially circularized Streptomyces chromosomes could not be mobilized by linear plasmids (SLP2 and SCP1), while linear chromosomes could. In comparison, a circular plasmid (pIJ303) could mobilize both circular and linear chromosomes at the same efficiencies. Interestingly, artificially circularized SLP2 exhibited partial self-transfer capability, indicating that, being a composite replicon, it may have acquired the additional internal origin of transfer from an ancestral circular plasmid during evolution.
authors: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan.
authors: Hsuan-Hsuan
authors: HH
authors: Lee
authors: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan.
authors: Chin-Chen
authors: CC
authors: Hsu
authors: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan.
authors: Yen-Ling
authors: YL
authors: Lin
authors: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan.
authors: Carton W
authors: CW
authors: Chen
mesh_terms: D002876:Chromosomes, Bacterial / Q000235:genetics* / Q000378:metabolism; D003227:Conjugation, Genetic / Q000235:genetics*; D004261:DNA Replication; D004270:DNA, Circular; D018390:Gene Targeting; D008957:Models, Genetic; D009154:Mutation / Q000235:genetics; D010957:Plasmids / Q000235:genetics* / Q000378:metabolism; D011995:Recombination, Genetic; D013302:Streptomyces / Q000235:genetics* / Q000378:metabolism; D016615:Telomere / Q000378:metabolism
chemical_list: D004270:DNA, Circular