Autoregulation of the partition genes of the mini-F plasmid and the intracellular localization of their products in Escherichia coli

Hirano, Mako; Mori, Hirotada; Onogi, Toshinari; Yamazoe, Mitsuyoshi; Niki, Hironori; Ogura, Teru; Hiraga, Sota

doi:10.1007/s004380050663

Cited by 68 publications

(66 citation statements)

References 38 publications

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“…Our main contribution is the finding that the P1 centromere analog, parS, can play an important, possibly catalytic role in that regulation. The P1 par operon is one of several partition operons that are regulated by the concerted action of both the proteins that they encode (24,29,30,32,33,35,47,55). Regulation of the partition operon of F appears also to be affected by the F-specific centromere sopC acting to enhance SopA-mediated repression (59).…”

Section: Discussionmentioning

confidence: 99%

Effects of the P1 Plasmid Centromere on Expression of P1 Partition Genes

Hao

Yarmolinsky

2002

J Bacteriol

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The partition operon of P1 plasmid encodes two proteins, ParA and ParB, required for the faithful segregation of plasmid copies to daughter cells. The operon is followed by a centromere analog, parS, at which ParB binds. ParA, a weak ATPase, represses the par promoter most effectively in its ADP-bound form. ParB can recruit ParA to parS, stimulate its ATPase, and significantly stimulate the repression. We report here that parS also participates in the regulation of expression of the par genes. A single chromosomal parS was shown to augment repression of several copies of the par promoter by severalfold. The repression increase was sensitive to the levels of ParA and ParB and to their ratio. The increase may be attributable to a conformational change in ParA mediated by the parS-ParB complex, possibly acting catalytically. We also observed an in cis effect of parS which enhanced expression of parB, presumably due to a selective modulation of the mRNA level. Although ParB had been earlier found to spread into and silence genes flanking parS, silencing of the par operon by ParB spreading was not significant. Based upon analogies between partitioning and septum placement, we speculate that the regulatory switch controlled by the parS-ParB complex might be essential for partitioning itself.Like many plasmids and chromosomes present in low copy numbers, plasmid prophage P1 is rarely lost at cell division. Its remarkable segregational stability is achieved by the mediation of partition proteins encoded by an operon of two genes. They act in conjunction with a cis-acting cluster of sites, parS, referred to as the plasmid centromere. Like many prokaryotic operons, the partition operon of P1 is regulated in a cooperative fashion by the proteins it encodes. The first protein of the operon, ParA, acts as repressor; the second, ParB, acts as corepressor (18).ParA binds in vitro to a region of 80 to 150 bp centered on a 20-bp imperfect palindrome overlapping the promoter, P par (9,11,29) (Fig.

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Section: Discussionmentioning

confidence: 99%

Effects of the P1 Plasmid Centromere on Expression of P1 Partition Genes

Hao

Yarmolinsky

2002

J Bacteriol

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“…The first task of a partition system is to identify its DNA cargo. SopB accomplishes this task by loading onto sopC and forming a partition complex, which has been visualized in vivo by fluorescence microscopy as punctuate foci (7,8). The partition complex is believed to contain a large number of SopB dimers, some bound specifically to sopC and additional dimers bound near sopC (9-11).…”

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Cell-free study of F plasmid partition provides evidence for cargo transport by a diffusion-ratchet mechanism

Vecchiarelli

Hwang

Mizuuchi

2013

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

138

185

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Increasingly diverse types of cargo are being found to be segregated and positioned by ParA-type ATPases. Several minimalistic systems described in bacteria are self-organizing and are known to affect the transport of plasmids, protein machineries, and chromosomal loci. One well-studied model is the F plasmid partition system, SopABC. In vivo, SopA ATPase forms dynamic patterns on the nucleoid in the presence of the ATPase stimulator, SopB, which binds to the sopC site on the plasmid, demarcating it as the cargo. To understand the relationship between nucleoid patterning and plasmid transport, we established a cell-free system to study plasmid partition reactions in a DNA-carpeted flowcell. We observed depletion zones of the partition ATPase on the DNA carpet surrounding partition complexes. The findings favor a diffusion-ratchet model for plasmid motion whereby partition complexes create an ATPase concentration gradient and then climb up this gradient toward higher concentrations of the ATPase. Here, we report on the dynamic properties of the Sop system on a DNA-carpet substrate, which further support the proposed diffusion-ratchet mechanism.bacterial chromosome segregation | ParA ATPase | plasmid segregation | spatial pattern organization | chromosome dynamics P roper DNA segregation ensures the faithful inheritance of genomic information for all life forms. In bacteria, this fundamental process is poorly understood. Low-copy bacterial genomes, including plasmids and chromosomes, encode active partition (Par) systems to ensure stability. Par systems are minimalistic in that only three dedicated components are required: a partition site on the DNA, a partition site-binding protein, and a nucleoside triphosphatase (NTPase). Par systems have been classified according to the type of NTPase involved: Walker-type (generically called "ParA"), actin-like, or tubulin-like (reviewed in ref. 1). Reconstitution of purified Par components of R1 plasmid in a cell-free system unveiled the mechanism involving an actin-like ATPase, ParM, in which elongating filaments of the ATPase push plasmids to opposite cell poles (2). Tubulin-like GTPases also appear to function as a filament (3). However, all chromosome-based and most plasmid-based systems use ParAs, and mounting evidence shows that ParA-like ATPases also are responsible for transporting large protein machineries (reviewed in ref. 4). However, the underlying mechanism for reactions of this category remains unresolved.The Sop system (stability of plasmid) of F plasmid is one of the first Par systems to be identified (5, 6) and is considered a paradigm for the study of ParA-mediated DNA segregation. The three plasmid-encoded system components are SopA (the ParAtype ATPase), SopB (or ParB in other systems; i.e., the partition site-binding protein), and sopC (or parS in other systems; i.e., the cis-acting partition site on the plasmid). The first task of a partition system is to identify its DNA cargo. SopB accomplishes this task by loading onto sopC and forming a partition c...

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“…Replication and resolution of progeny plasmid molecules, and resealing to CCC form, must be completed before gyrase introduces supercoils (49). Because much of cell's SopB is concentrated at extended partition complexes (3,50), reassembly of new complexes after replication of sopC could occur quickly and allow extension of the complexes before the onset of supercoiling, resulting in a zone impervious to gyrase. We assume that the SopB-SopB interactions responsible for attracting SopB to the sopC flanks generate a structure compact enough to resist transmission of topological changes occurring in the SopB-free region of the plasmid.…”

Section: Discussionmentioning

confidence: 99%

“…The dynamics of ParA proteins stem from their ability to form metastable polymers. In vivo, dynamic behavior is seen only if the cognate ParB and centromere are both present (2); ParB proteins, though able to interact with ParA (3,4) and to stimulate ATP hydrolysis (5,6), do not alone promote ParA dynamics. Some aspect of partition complex structure appears to be needed to explain this key event in partition.…”

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Molecular Basis of the Supercoil Deficit Induced by the Mini-F Plasmid Partition Complex

Bouet

Lane

2009

Journal of Biological Chemistry

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Formation of a partition complex on plasmid F by binding of SopB protein to the sopC centromere is the first step in the partition process that ensures stability of F in dividing cells. Establishment of the complex enables nonspecific binding of SopB to neighboring DNA, which extends the partition complex and provokes reduction of negative supercoiling of the plasmid. This reduction is believed to reflect winding of DNA into positive supercoils about SopB to create a nucleoprotein structure of probable importance to partition. We have searched for evidence that SopB alters plasmid topology. Permutation analysis indicated only modest bending of linear DNA fragments, and in vivo DNase I footprinting revealed no enhanced cleavages indicating curvature. In vitro, SopB binding left no topological trace in relaxed-circular DNA treated with topoisomerase I or in nicked circles closed by ligase. In vivo, novobiocin-mediated inhibition of DNA gyrase relaxed a plasmid carrying the partition complex but left no residue of positive supercoils. Hence, SopB does not reduce plasmid supercoiling directly. We did observe that SopB partly prevented removal of negative supercoils from plasmid DNA by topoisomerase I and partly prevented ligation of nicked circles, indicating that it acts as a physical obstacle. The supercoil deficit is thus better explained as SopB recoating of just-replicated DNA, which shelters it from gyrase and from topological changes in SopB-free DNA. This topological simplicity distinguishes the Sop partition complex from other complexes described.

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Autoregulation of the partition genes of the mini-F plasmid and the intracellular localization of their products in Escherichia coli

Cited by 68 publications

References 38 publications

Effects of the P1 Plasmid Centromere on Expression of P1 Partition Genes

Effects of the P1 Plasmid Centromere on Expression of P1 Partition Genes

Cell-free study of F plasmid partition provides evidence for cargo transport by a diffusion-ratchet mechanism

Molecular Basis of the Supercoil Deficit Induced by the Mini-F Plasmid Partition Complex

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