title: Condensin promotes the juxtaposition of DNA flanking its loading site in Bacillus subtilis.
abstract: SMC condensin complexes play a central role in compacting and resolving replicated chromosomes in virtually all organisms, yet how they accomplish this remains elusive. In Bacillus subtilis, condensin is loaded at centromeric parS sites, where it encircles DNA and individualizes newly replicated origins. Using chromosome conformation capture and cytological assays, we show that condensin recruitment to origin-proximal parS sites is required for the juxtaposition of the two chromosome arms. Recruitment to ectopic parS sites promotes alignment of large tracks of DNA flanking these sites. Importantly, insertion of parS sites on opposing arms indicates that these "zip-up" interactions only occur between adjacent DNA segments. Collectively, our data suggest that condensin resolves replicated origins by promoting the juxtaposition of DNA flanking parS sites, drawing sister origins in on themselves and away from each other. These results are consistent with a model in which condensin encircles the DNA flanking its loading site and then slides down, tethering the two arms together. Lengthwise condensation via loop extrusion could provide a generalizable mechanism by which condensin complexes act dynamically to individualize origins in B. subtilis and, when loaded along eukaryotic chromosomes, resolve them during mitosis.
authors.affiliation: Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts 02115, USA;
authors.forename: Xindan
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;
authors.forename: Tung B K
authors.initials: TB
authors.lastname: Le
authors.affiliation: Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA;
authors.forename: Bryan R
authors.initials: BR
authors.lastname: Lajoie
authors.affiliation: Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA;
authors.forename: Job
authors.initials: J
authors.lastname: Dekker
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Laub
authors.affiliation: Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts 02115, USA;
authors.forename: David Z
authors.initials: DZ
authors.lastname: Rudner
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism*; D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism*; D002876:Chromosomes, Bacterial / Q000235:genetics*; D019915:DNA Primase / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics* / Q000378:metabolism*; D009698:Nucleoproteins / Q000378:metabolism; D018741:Replication Origin
chemical_list: D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; D009698:Nucleoproteins; C108312:condensin complexes; D019915:DNA Primase; D000251:Adenosine Triphosphatases
keywords: DNA segregation; Hi-C; ParB; SMC; lengthwise condensation; mitosis; parS