The SMC condensin complex is required for origin segregation in Bacillus subtilis.
SMC condensin complexes play a central role in organizing and compacting chromosomes in all domains of life [1, 2]. In the bacterium Bacillus subtilis, cells lacking SMC are viable only during slow growth and display decondensed chromosomes, suggesting that SMC complexes function throughout the genome [3, 4]. Here, we show that rapid inactivation of SMC or its partner protein ScpB during fast growth leads to a failure to resolve newly replicated origins and a complete block to chromosome segregation. Importantly, the loss of origin segregation is not due to an inability to unlink precatenated sister chromosomes by Topoisomerase IV. In support of the idea that ParB-mediated recruitment of SMC complexes to the origin is important for their segregation, cells with reduced levels of SMC that lack ParB are severely impaired in origin resolution. Finally, we demonstrate that origin segregation is a task shared by the condensin complex and the parABS partitioning system. We propose that origin-localized SMC constrains adjacent DNA segments along their lengths, drawing replicated origins in on themselves and away from each other. This SMC-mediated lengthwise condensation, bolstered by the parABS system, drives origin segregation.
Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston MA 02115, USA.
Xindan
X
Wang
Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston MA 02115, USA.
Olive W
OW
Tang
Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston MA 02115, USA.
Eammon P
EP
Riley
Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston MA 02115, USA. Electronic address: rudner@hms.harvard.edu.
David Z
DZ
Rudner
D000251:Adenosine Triphosphatases / Q000378:metabolism; D001412:Bacillus subtilis / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D020090:Chromosome Segregation / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008938:Mitosis / Q000502:physiology*; D046912:Multiprotein Complexes / Q000378:metabolism; D018741:Replication Origin / Q000502:physiology
D001426:Bacterial Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; C118650:SMC protein, Bacteria; C509375:ScpA protein, Bacillus subtilis; C108312:condensin complexes; D000251:Adenosine Triphosphatases