SMC condensin entraps chromosomal DNA by an ATP hydrolysis dependent loading mechanism in Bacillus subtilis

• Published in: eLife Vol. 4
• Main Authors: Wilhelm, Larissa, Bürmann, Frank, Minnen, Anita, Shin, Ho-Chul, Toseland, Christopher P, Oh, Byung-Ha, Gruber, Stephan
• Format: Journal Article
• Language: English
• Published: England eLife Sciences Publications Ltd 07-05-2015; eLife Sciences Publications, Ltd
• Subjects: Adenosine triphosphatase; Adenosine Triphosphatases - metabolism; Adenosine Triphosphate - biosynthesis; Bacillus subtilis; Bacterial Proteins - metabolism; Biochemistry; Cell cycle; Cell Cycle Proteins - metabolism; Cell division; chromosome condensation; chromosome segregation; Chromosomes; Chromosomes, Bacterial - genetics; Condensin; Deoxyribonucleic acid; DNA; DNA, Bacterial - metabolism; DNA-Binding Proteins - metabolism; Enzymes; Genes and Chromosomes; Hydrolysis; Interfaces; Microscopy; Multiprotein Complexes - metabolism; ParB protein; Proteins; Replication origins; sliding clamp; Smc protein; Streptococcus infections; B. subtilis; condensin; Smc proteins; chromosome segregation; genes; biochemistry; chromosomes; sliding clamp; ParB protein; chromosome condensation
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/elife.06659

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.