SMC condensin entraps chromosomal DNA by an ATP hydrolysis dependent loading mechanism in Bacillus subtilis
Larissa Wilhelm,
Frank Bürmann,
Anita Minnen,
Ho-Chul Shin,
Christopher P Toseland,
Byung-Ha Oh,
Stephan Gruber
Affiliations
Larissa Wilhelm
Chromosome Organization and Dynamics, Max Planck Institute of Biochemistry, Martinsried, Germany
Frank Bürmann
Chromosome Organization and Dynamics, Max Planck Institute of Biochemistry, Martinsried, Germany
Anita Minnen
Chromosome Organization and Dynamics, Max Planck Institute of Biochemistry, Martinsried, Germany
Ho-Chul Shin
Department of Biological Sciences, KAIST Institute for the Biocentury, Cancer Metastasis Control Center, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
Christopher P Toseland
Chromosome Organization and Dynamics, Max Planck Institute of Biochemistry, Martinsried, Germany
Byung-Ha Oh
Department of Biological Sciences, KAIST Institute for the Biocentury, Cancer Metastasis Control Center, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
Stephan Gruber
Chromosome Organization and Dynamics, Max Planck Institute of Biochemistry, Martinsried, Germany
Smc–ScpAB forms elongated, annular structures that promote chromosome segregation, presumably by compacting and resolving sister DNA molecules. The mechanistic basis for its action, however, is only poorly understood. Here, we have established a physical assay to determine whether the binding of condensin to native chromosomes in Bacillus subtilis involves entrapment of DNA by the Smc–ScpAB ring. To do so, we have chemically cross-linked the three ring interfaces in Smc–ScpAB and thereafter isolated intact chromosomes under protein denaturing conditions. Exclusively species of Smc–ScpA, which were previously cross-linked into covalent rings, remained associated with chromosomal DNA. DNA entrapment is abolished by mutations that interfere with the Smc ATPase cycle and strongly reduced when the recruitment factor ParB is deleted, implying that most Smc–ScpAB is loaded onto the chromosome at parS sites near the replication origin. We furthermore report a physical interaction between native Smc–ScpAB and chromosomal DNA fragments.