Abstract
The segregation of newly replicated chromosomes in bacterial cells is a highly coordinated spatiotemporal process. In the majority of bacterial species, a tripartite ParAB-parS system, composed of an ATPase (ParA), a DNA-binding protein (ParB), and its target(s) parS sequence(s), facilitates the initial steps of chromosome partitioning. ParB nucleates around parS(s) located in the vicinity of newly replicated oriCs to form large nucleoprotein complexes, which are subsequently relocated by ParA to distal cellular compartments. In this review, we describe the role of ParB in various processes within bacterial cells, pointing out interspecies differences. We outline recent progress in understanding the ParB nucleoprotein complex formation and its role in DNA segregation, including ori positioning and anchoring, DNA condensation, and loading of the structural maintenance of chromosome (SMC) proteins. The auxiliary roles of ParBs in the control of chromosome replication initiation and cell division, as well as the regulation of gene expression, are discussed. Moreover, we catalog ParB interacting proteins. Overall, this work highlights how different bacterial species adapt the DNA partitioning ParAB-parS system to meet their specific requirements.
Highlights
Bacterial genomes consist of circular or linear and single or multiple chromosomes as well as extra-chromosomal elements like plasmids
We summarize our current understanding of chromosomal ParAB-parS partition systems, which are involved in ori positioning in many species
Our analysis of available ChIP-seq data showed that binding to parS half-sites GTTCCAC and GTTTCAC is not a unique feature of P. aeruginosa ParB
Summary
Bacterial genomes consist of circular or linear and single or multiple chromosomes as well as extra-chromosomal elements like plasmids. A bi-directional, semi-conservative replication initiated from oriC proceeds simultaneously with the segregation of compacted daughter nucleoids Specific factors, such as DNA supercoiling, and proteins, such as nucleoid associated proteins (NAPs), determine, maintain, and modify the spatial organization of bacterial nucleoids during the entire cell cycle, from the initiation of replication to the end of the division cycle (reviewed in [2,10,11,12]). Chromosomes in most rod-like bacteria, including B. subtilis, C. crescentus, Pseudomonas aeruginosa, Vibrio cholerae, and Myxococcus xanthus, adopt longitudinal organization In this arrangement, the two replication arms align along the long axis of the cell, whereas the ori and ter domains locate at opposite cell ends [9,16,28,30,31]. We catalog ParB interacting proteins from various species, which indicates that the biological roles of ParAB-parS systems may extend far beyond the chromosome segregation process
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