<i>par</i>
            genes and the pathology of chromosome loss in
            <i>Vibrio cholerae</i>

Yamaichi, Yoshiharu; Fogel, Michael; Waldor, Matthew K.

doi:10.1073/pnas.0608341104

Cited by 91 publications

(115 citation statements)

References 41 publications

(56 reference statements)

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“…Chromosomally encoded par loci are composed of an ATPase (ParA), a DNA binding protein (ParB), and a centromere-like sequence (parS) (39). All three are critical for origin segregation in C. crescentus (40,41), Pseudomonas aeruginosa (42), and V. cholerae chromosome II (43). In B. subtilis, cells lacking ParA, called Soj, have a very mild defect in chromosome segregation (23).…”

Section: Partitioning Locus Helps Establish and Maintain The Origins mentioning

confidence: 99%

Bacillus subtilischromosome organization oscillates between two distinct patterns

Wang

Llopis

Rudner

2014

Proc. Natl. Acad. Sci. U.S.A.

116

146

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Bacterial chromosomes have been found to possess one of two distinct patterns of spatial organization. In the first, called "ori-ter" and exemplified by Caulobacter crescentus, the chromosome arms lie side-by-side, with the replication origin and terminus at opposite cell poles. In the second, observed in slow-growing Escherichia coli ("left-ori-right"), the two chromosome arms reside in separate cell halves, on either side of a centrally located origin. These two patterns, rotated 90°relative to each other, appear to result from different segregation mechanisms. Here, we show that the Bacillus subtilis chromosome alternates between them. For most of the cell cycle, newly replicated origins are maintained at opposite poles with chromosome arms adjacent to each other, in an ori-ter configuration. Shortly after replication initiation, the duplicated origins move as a unit to midcell and the two unreplicated arms resolve into opposite cell halves, generating a left-ori-right pattern. The origins are then actively segregated toward opposite poles, resetting the cycle. Our data suggest that the condensin complex and the parABS partitioning system are the principal driving forces underlying this oscillatory cycle. We propose that the distinct organization patterns observed for bacterial chromosomes reflect a common organization-segregation mechanism, and that simple modifications to it underlie the unique patterns observed in different species.DNA replication | ParA | chromosome segregation | SMC condensin C entral to reproduction is the faithful segregation of replicated chromosomes to daughter cells. In eukaryotes, DNA replication, chromosome condensation, and sister chromatid segregation are separated into distinct steps in the cell cycle that are safeguarded by checkpoint pathways. In bacteria, these processes occur concurrently, posing unique challenges to genome integrity and inheritance (1, 2). In the absence of temporal control, bacteria take advantage of spatial organization to promote faithful and efficient chromosome segregation. The organization of the chromosome dictates where the chromosome is replicated, and the factors that organize and compact the newly replicated DNA play a central role in its segregation (1, 2).Studies in different bacteria have revealed strikingly distinct patterns of chromosome organization that appear to arise from different segregation mechanisms. In Caulobacter crescentus and Vibrio cholerae chromosome I, the origin and terminus are located at opposite cell poles, with the two replication arms between them, in a pattern referred to as "ori-ter" (3-5). After replication initiation, one of the sister origins is held in place and the other is actively translocated to the opposite cell pole, regenerating the oriter organization in both daughter cells (5-11). By contrast, in slowgrowing Escherichia coli, the origin is located in the middle of the nucleoid and the two replication arms reside in opposite cell halves, in a "left-ori-right" pattern (12, 13). Replication initiates at mid...

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Section: Partitioning Locus Helps Establish and Maintain The Origins mentioning

confidence: 99%

Bacillus subtilischromosome organization oscillates between two distinct patterns

Wang

Llopis

Rudner

2014

Proc. Natl. Acad. Sci. U.S.A.

116

146

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“…In contrast, these systems are essential for viability in C. crescentus (41,54) and for segregation of chromosome II in V. cholerae (63). The latter requirement may be due to the fact that chromosome II has many properties of a large plasmid and its Par proteins are more closely related to plasmid-encoded ones than to those encoded on chromosomes (22).…”

mentioning

confidence: 99%

Independent Segregation of the Two Arms of theEscherichia coli oriRegion Requires neither RNA Synthesis nor MreB Dynamics

Wang

Sherratt

2010

J Bacteriol

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The mechanism of Escherichia coli chromosome segregation remains elusive. We present results on the simultaneous tracking of segregation of multiple loci in the ori region of the chromosome in cells growing under conditions in which a single round of replication is initiated and completed in the same generation. Loci segregated as expected for progressive replication-segregation from oriC, with markers placed symmetrically on either side of oriC segregating to opposite cell halves at the same time, showing that sister locus cohesion in the origin region is local rather than extensive. We were unable to observe any influence on segregation of the proposed centromeric site, migS, or indeed any other potential cis-acting element on either replication arm (replichore) in the AB1157 genetic background. Site-specific inhibition of replication close to oriC on one replichore did not prevent segregation of loci on the other replichore. Inhibition of RNA synthesis and inhibition of the dynamic polymerization of the actin homolog MreB did not affect ori and bulk chromosome segregation.The chromosome of the extensively studied bacterium Escherichia coli undergoes simultaneous replication and segregation and has no apparent mitotic apparatus for chromosome segregation, a situation very different from that of eukaryotes, where replication and segregation occur in temporally separate periods of the cell cycle. An unsolved mystery of the bacterial cell cycle is how chromosome segregation takes place. Several mechanisms have been proposed to drive the segregation of origin and bulk DNA after replication. In one model, cell elongation is proposed to be a crucial factor, in which the two newly replicated origins are attached to the inner membrane and separated by cell growth between them along the long axis of the cell (25). However, it is now clear that elongation occurs throughout the cell and the movement of the origins is much faster than the rate of cell elongation, indicating that cell elongation alone is not responsible for segregation (55,60).Active partitioning systems were first found in low-copynumber plasmids, where they are required for stable inheritance by distributing the daughter plasmids to both daughter cells (reviewed in reference 14). These systems fall into two families; one uses the ParM actin and its associated protein and binding sites to drive newly replicated sister plasmids apart during cycles of actin polymerization and depolymerization (4, 19). The second parABS family is less well understood mechanistically, although ATP hydrolysis-dependent cycles of ParA movement appear to play a key role in the segregation process (48).Later, it was found that many bacterial chromosomes also utilize parABS systems for their segregation, for example, Bacillus subtilis (23, 37), Caulobacter crescentus (41), and both chromosomes of Vibrio cholerae (22). The typical chromosomal par locus consists of two genes, parA and parB (soj and spo0J in B. subtilis), and a cis-acting parS DNA element. ParB is a DNA-binding prote...

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“…Although chromosomal parABS (chr-parABS) elements are phylogenetically distinct from those found in plasmids (13), inactivating or overexpressing chr-parABS components in several species leads to elevated numbers of anucleate cells (14)(15)(16) and introduction of chr-parABS stabilizes plasmids in heterologous hosts (17)(18)(19). In vivo observations of Vibrio cholerae's chromosome I dynamics suggested a mechanism by which ParAI (chromosome I's cognate ParA) pulls on the ParBI/parSI complex to effect chromosome segregation (20).…”

mentioning

confidence: 99%

“…However, although the absence of parAI in V. cholerae alters chromosome segregation, growth is not affected (19,20). Indeed, despite widespread conservation of the parS sequence, except for V. cholerae chromosome II and Caulobacter crescentus (henceforth, Caulobacter), the absence of parABS elements only mildly impairs growth (18,21), suggesting the presence of redundant chromosome segregation mechanisms (8,(22)(23)(24).…”

mentioning

confidence: 99%

Caulobacter requires a dedicated mechanism to initiate chromosome segregation

Toro

Hong

McAdams

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

156

241

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Chromosome segregation in bacteria is rapid and directed, but the mechanisms responsible for this movement are still unclear. We show that Caulobacter crescentus makes use of and requires a dedicated mechanism to initiate chromosome segregation. Caulobacter has a single circular chromosome whose origin of replication is positioned at one cell pole. Upon initiation of replication, an 8-kb region of the chromosome containing both the origin and parS moves rapidly to the opposite pole. This movement requires the highly conserved ParABS locus that is essential in Caulobacter. We use chromosomal inversions and in vivo time-lapse imaging to show that parS is the Caulobacter site of force exertion, independent of its position in the chromosome. When parS is moved farther from the origin, the cell waits for parS to be replicated before segregation can begin. Also, a mutation in the ATPase domain of ParA halts segregation without affecting replication initiation. Chromosome segregation in Caulobacter cannot occur unless a dedicated parS guiding mechanism initiates movement.centromere ͉ parS ͉ ParA

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par genes and the pathology of chromosome loss in Vibrio cholerae

Cited by 91 publications

References 41 publications

Bacillus subtilischromosome organization oscillates between two distinct patterns

Bacillus subtilischromosome organization oscillates between two distinct patterns

Independent Segregation of the Two Arms of theEscherichia coli oriRegion Requires neither RNA Synthesis nor MreB Dynamics

Caulobacter requires a dedicated mechanism to initiate chromosome segregation

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