Stochastic Self-Assembly of ParB Proteins Builds the Bacterial DNA Segregation Apparatus

Many canonical processes in molecular biology rely on the dynamic assembly of higher-order nucleoprotein complexes. In bacteria, the assembly mechanism of ParABS, the nucleoprotein super-complex that actively segregates the bacterial chromosome and many plasmids, remains elusive. We combined super-r...

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Bibliographic Details
Published in:Cell systems 2015-08, Vol.1 (2), p.163-173
Main Authors: Sanchez, Aurore, Cattoni, Diego I., Walter, Jean-Charles, Rech, Jérôme, Parmeggiani, Andrea, Nollmann, Marcelo, Bouet, Jean-Yves
Format: Article
Language:English
Subjects:
Biochemistry, Molecular Biology
Biological Physics
Biophysics
Life Sciences
Molecular biology
Physics
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Summary:Many canonical processes in molecular biology rely on the dynamic assembly of higher-order nucleoprotein complexes. In bacteria, the assembly mechanism of ParABS, the nucleoprotein super-complex that actively segregates the bacterial chromosome and many plasmids, remains elusive. We combined super-resolution microscopy, quantitative genome-wide surveys, biochemistry, and mathematical modeling to investigate the assembly of ParB at the centromere-like sequences parS. We found that nearly all ParB molecules are actively confined around parS by a network of synergistic protein-protein and protein-DNA interactions. Interrogation of the empirically determined, high-resolution ParB genomic distribution with modeling suggests that instead of binding only to specific sequences and subsequently spreading, ParB binds stochastically around parS over long distances. We propose a new model for the formation of the ParABS partition complex based on nucleation and caging: ParB forms a dynamic lattice with the DNA around parS. This assembly model and approach to characterizing large-scale, dynamic interactions between macromolecules may be generalizable to many unrelated machineries that self-assemble in superstructures. [Display omitted] •From PALM, more than 90% of ParB proteins are actively confined at parS sites•A network of three synergistic, independent interactions drives ParB confinement•Stochastic binding to non-specific DNA organizes the partition complex in space•A nucleation and caging mechanism describes the dynamic assembly near parS sites Sanchez et al. use super-resolution microscopy, modeling, and classical biochemistry to investigate the assembly mechanism of the bacterial partition complex ParB on centromeric DNA. They propose a new model, termed nucleation and caging, for ParB self-assembly; it involves stochastic binding and active confinement of ParBs on DNA near the centromere.
ISSN:2405-4712
2405-4720
DOI:10.1016/j.cels.2015.07.013