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Mol Syst Biol. 2018 Nov 16;14(11):e8516. doi: 10.15252/msb.20188516.

A conserved mechanism drives partition complex assembly on bacterial chromosomes and plasmids.

Author information

1
Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Centre National de la Recherche Scientifique (CNRS), Université de Toulouse, UPS, Toulouse, France.
2
LISBP, CNRS, INRA, INSA, Université de Toulouse, Toulouse, France.
3
Laboratoire Charles Coulomb, CNRS-Université Montpellier, Montpellier, France.
4
Dynamique des Interactions Membranaires Normales et Pathologiques, CNRS-Université Montpellier, Montpellier, France.
5
Laboratoire Charles Coulomb, CNRS-Université Montpellier, Montpellier, France jean-charles.walter@umontpellier.fr jean-yves.bouet@ibcg.biotoul.fr.
6
Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Centre National de la Recherche Scientifique (CNRS), Université de Toulouse, UPS, Toulouse, France jean-charles.walter@umontpellier.fr jean-yves.bouet@ibcg.biotoul.fr.

Abstract

Chromosome and plasmid segregation in bacteria are mostly driven by ParABS systems. These DNA partitioning machineries rely on large nucleoprotein complexes assembled on centromere sites (parS). However, the mechanism of how a few parS-bound ParB proteins nucleate the formation of highly concentrated ParB clusters remains unclear despite several proposed physico-mathematical models. We discriminated between these different models by varying some key parameters in vivo using the F plasmid partition system. We found that "Nucleation & caging" is the only coherent model recapitulating in vivo data. We also showed that the stochastic self-assembly of partition complexes (i) is a robust mechanism, (ii) does not directly involve ParA ATPase, (iii) results in a dynamic structure of discrete size independent of ParB concentration, and (iv) is not perturbed by active transcription but is by protein complexes. We refined the "Nucleation & caging" model and successfully applied it to the chromosomally encoded Par system of Vibrio cholerae, indicating that this stochastic self-assembly mechanism is widely conserved from plasmids to chromosomes.

KEYWORDS:

Escherichia coli ; DNA segregation; F plasmid; ParABS; plasmid partition

PMID:
30446599
PMCID:
PMC6238139

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