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In vivo Assembly of Bacterial Partition Condensates on Supercoiled and Linear DNA
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  • Hicham Sekkouri Alaoui,
  • Valentin Quèbre,
  • Linda Delimi,
  • Jérôme Rech,
  • Roxanne Debaugny-Diaz,
  • Delphine Labourdette,
  • Manuel Campos,
  • François Cornet,
  • J-C. Walter,
  • J.Y. Bouet
Hicham Sekkouri Alaoui
Universite Toulouse III-Paul Sabatier
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Valentin Quèbre
Universite Toulouse III-Paul Sabatier
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Linda Delimi
Universite de Montpellier Faculte de Medecine Montpellier-Nimes
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Jérôme Rech
Universite Toulouse III-Paul Sabatier
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Roxanne Debaugny-Diaz
Universite Toulouse III-Paul Sabatier
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Delphine Labourdette
INSA Toulouse
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Manuel Campos
Universite Toulouse III-Paul Sabatier
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François Cornet
Universite Toulouse III-Paul Sabatier
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J-C. Walter
Universite de Montpellier Faculte de Medecine Montpellier-Nimes
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J.Y. Bouet
Universite Toulouse III-Paul Sabatier

Corresponding Author:[email protected]

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Abstract

In bacteria, faithful DNA segregation of chromosomes and plasmids is mainly mediated by ParABS systems. These systems, consisting of a ParA ATPase, a DNA binding ParB CTPase, and centromere sites parS, orchestrate the separation of newly replicated DNA copies and their intracellular positioning. Accurate segregation relies on the assembly of a high-molecular-weight complex, comprising a few hundreds of ParB dimers nucleated from parS sites. This complex assembles in a multi-step process and exhibits dynamic liquid-droplet properties. Despite various proposed models, the complete mechanism for partition complex assembly remains elusive. This study investigates the impact of DNA supercoiling on ParB DNA binding profiles in vivo, using the ParABS system of the plasmid F. We found that variations in DNA supercoiling does not significantly affect any steps in the assembly of the partition complex. Furthermore, physical modeling, leveraging ChIP-seq data from linear plasmids F, suggests that ParB sliding is restricted to approximately 2-Kbp from parS, highlighting the necessity for additional mechanisms beyond ParB sliding over DNA for concentrating ParB into condensates nucleated at parS. Lastly, explicit simulations of a polymer coated with bound ParB suggest a dominant role for ParB-ParB interactions in DNA compaction within ParB condensates.
16 Apr 2024Submission Checks Completed
16 Apr 2024Assigned to Editor
16 Apr 2024Reviewer(s) Assigned
11 May 2024Review(s) Completed, Editorial Evaluation Pending