Interlinked sister chromosomes arise in the absence of condensin during fast replication in B. subtilis.
Condensin-an SMC-kleisin complex-is essential for efficient segregation of sister chromatids in eukaryotes [1-4]. In Escherichia coli and Bacillus subtilis, deletion of condensin subunits results in severe growth phenotypes and the accumulation of cells lacking nucleoids [5, 6]. In many other bacteria and under slow growth conditions, however, the reported phenotypes are much milder or virtually absent [7-10]. This raises the question of what role prokaryotic condensin might play during chromosome segregation under various growth conditions. In B. subtilis and Streptococcus pneumoniae, condensin complexes are enriched on the circular chromosome near the single origin of replication by ParB proteins bound to parS sequences [11, 12]. Using conditional alleles of condensin in B. subtilis, we demonstrate that depletion of its activity results in an immediate and severe defect in the partitioning of replication origins. Multiple copies of the chromosome remain unsegregated at or near the origin of replication. Surprisingly, the growth and chromosome segregation defects in rich medium are suppressed by a reduction of replication fork velocity but not by partial inhibition of translation or transcription. Prokaryotic condensin likely prevents the formation of sister DNA interconnections at the replication fork or promotes their resolution behind the fork.
Max Planck Institute of Biochemistry, Research Group "Chromosome Organization and Dynamics," Am Klopferspitz 18, 82152 Martinsried, Germany; Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle Upon Tyne NE2 4AX, UK. Electronic address: sgruber@biochem.mpg.de.
Stephan
S
Gruber
Molecular Genetics Group, Groningen Biomolecular Sciences and Biotechnology Institute, Centre for Synthetic Biology, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands; Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle Upon Tyne NE2 4AX, UK.
Jan-Willem
JW
Veening
Department of Biology I, Ludwig Maximilians University, Munich, Großhaderner Str. 2-4, 82152 Martinsried, Germany.
Juri
J
Bach
Max Planck Institute of Biochemistry, Research Group "Chromosome Organization and Dynamics," Am Klopferspitz 18, 82152 Martinsried, Germany.
Martin
M
Blettinger
Department of Biology I, Ludwig Maximilians University, Munich, Großhaderner Str. 2-4, 82152 Martinsried, Germany.
Marc
M
Bramkamp
Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle Upon Tyne NE2 4AX, UK. Electronic address: jeff.errington@newcastle.ac.uk.
Jeff
J
Errington
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001412:Bacillus subtilis / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism*; D020090:Chromosome Segregation / Q000502:physiology*; D002876:Chromosomes, Bacterial / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism*; D018741:Replication Origin / Q000502:physiology*
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; C108312:condensin complexes; D000251:Adenosine Triphosphatases