Abstract
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.
Article and author information
Author details
Reviewing Editor
- Bernard de Massy, Institute of Human Genetics, CNRS UPR 1142, France
Publication history
- Received: January 25, 2015
- Accepted: May 6, 2015
- Accepted Manuscript published: May 7, 2015 (version 1)
- Accepted Manuscript updated: May 8, 2015 (version 2)
- Version of Record published: May 26, 2015 (version 3)
Copyright
© 2015, Wilhelm et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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