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Mechanics of DNA bridging by bacterial condensin MukBEF in vitro and in singulo
Author(s) -
Petrushenko Zoya M,
Cui Yuanbo,
She Weifeng,
Rybenkov Valentin V
Publication year - 2010
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2009.414
Subject(s) - biology , condensin , dna , bridging (networking) , biophysics , microbiology and biotechnology , genetics , chromosome , circular bacterial chromosome , chromosome segregation , computational biology , chromatin , dna replication , cohesin , gene , computer science , computer network
Structural maintenance of chromosome (SMC) proteins comprise the core of several specialized complexes that stabilize the global architecture of the chromosomes by dynamically linking distant DNA fragments. This reaction however remains poorly understood giving rise to numerous proposed mechanisms of the proteins. Using two novel assays, we investigated real‐time formation of DNA bridges by bacterial condensin MukBEF. We report that MukBEF can efficiently bridge two DNAs and that this reaction involves multiple steps. The reaction begins with the formation of a stable MukB–DNA complex, which can further capture another protein‐free DNA fragment. The initial tether is unstable but is quickly strengthened by additional MukBs. DNA bridging is modulated but is not strictly dependent on ATP and MukEF. The reaction revealed high preference for right‐handed DNA crossings indicating that bridging involves physical association of MukB with both DNAs. Our data establish a comprehensive view of DNA bridging by MukBEF, which could explain how SMCs establish both intra‐ and interchromosomal links inside the cell and indicate that DNA binding and bridging could be separately regulated.