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Molecular characterization of a bacterial DNA segregation apparatus

Abstract : The active partition of low copy number plasmids and most bacterial chromosomes relies on the assembly of a nucleoprotein superstructure nucleated at centromere-like sites near the origin of replication. In the case of type I partition systems, the most widespread on plasmids and the only ones present on chromosomes, centromere binding proteins, ParB, display the capability to propagate along DNA from their nucleation point at the centromere-like site, parS. This structure, termed the partition complex, contains over 90% of the available ParB in the cell and interacts with ParA, a ParB- and DNA-dependent ATPase, to segregate and position replicons within the cell. Two concurrent models exist to explain the assembly mechanism of the partition complex: the spreading and bridging (Graham et al., 2014), and the nucleation and caging (Sanchez et al., 2015) models. We used the partition system of the archetypal plasmid F and the naturally occurring partition system of Vibrio cholerae's chromosome 1. First, we explored the mechanisms of centromere-based incompatibilities to gain insight into partition complex assembly in low levels of ParB through parS titration of ParB. Next, we describe an optimized a high- resolution ChIP-sequencing protocol from the lab bench to data analysis. Then, through ChIP-sequencing, epifluorescence microscopy and physico-mathematical modeling, we revealed that the partition complex assembly mechanism is robust and consistent with the nucleation and caging model on both chromosomal and plasmid systems.
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https://tel.archives-ouvertes.fr/tel-01945264
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Submitted on : Wednesday, December 5, 2018 - 11:14:06 AM
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Roxanne Diaz. Molecular characterization of a bacterial DNA segregation apparatus. Microbiology and Parasitology. Université Paul Sabatier - Toulouse III, 2017. English. ⟨NNT : 2017TOU30311⟩. ⟨tel-01945264⟩

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