Towards understanding the molecular basis of bacterial DNA segregation

Leonard, Thomas A.; Møller‐Jensen, Jakob; Löwe, Jan

doi:10.1098/rstb.2004.1608

Cited by 66 publications

(97 citation statements)

References 134 publications

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“…Treadmilling models are based upon the two ends of a filament being different, where one end is growing and the other depolymerizing. Such treadmilling of ParA2 could move the DNA to which the ParA2 filament is bound only if ParA2 were also bound to a fixed host factor (43). However, the bipolar nature of the ParA2-DNA filament that we observed suggests that such models are unlikely, or that any polarity must be conferred by one end of the filament being in contact with ParB2 or some other as yet undetermined element.…”

Section: Discussioncontrasting

confidence: 38%

ParA2, aVibrio choleraechromosome partitioning protein, forms left-handed helical filaments on DNA

Hui

Galkin²,

Xiong³

et al. 2010

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

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Most bacterial chromosomes contain homologs of plasmid partitioning (par) loci. These loci encode ATPases called ParA that are thought to contribute to the mechanical force required for chromosome and plasmid segregation. In Vibrio cholerae, the chromosome II (chrII) par locus is essential for chrII segregation. Here, we found that purified ParA2 had ATPase activities comparable to other ParA homologs, but, unlike many other ParA homologs, did not form high molecular weight complexes in the presence of ATP alone. Instead, formation of high molecular weight ParA2 polymers required DNA. Electron microscopy and three-dimensional reconstruction revealed that ParA2 formed bipolar helical filaments on double-stranded DNA in a sequence-independent manner. These filaments had a distinct change in pitch when ParA2 was polymerized in the presence of ATP versus in the absence of a nucleotide cofactor. Fitting a crystal structure of a ParA protein into our filament reconstruction showed how a dimer of ParA2 binds the DNA. The filaments formed with ATP are left-handed, but surprisingly these filaments exert no topological changes on the right-handed B-DNA to which they are bound. The stoichiometry of binding is one dimer for every eight base pairs, and this determines the geometry of the ParA2 filaments with 4.4 dimers per 120 Å pitch left-handed turn. Our findings will be critical for understanding how ParA proteins function in plasmid and chromosome segregation.nucleoprotein filament | DNA segregation

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Section: Discussioncontrasting

confidence: 38%

ParA2, aVibrio choleraechromosome partitioning protein, forms left-handed helical filaments on DNA

Hui

Galkin²,

Xiong³

et al. 2010

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

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“…The structure of the proU::tet lesion was confirmed by PCR and DNA sequencing (GATC Biotech) and then used as a template for the insertion of the modified icsB-proU-gfp-cat promoters using primer set icsB.fw. 40 ␤-Galactosidase assay. The transcription of the mxiC::lacZ fusion was measured in cultures of the wild type and hns and virB mutant strains grown overnight in LO or LB broth at 37°C.…”

Section: Methodsmentioning

confidence: 99%

“…ParB-like proteins bind to a cis-acting DNA sequence called parS (5,28,35,40,67,70), and it has been found that the VirB binding site at the icsB promoter retains the features of a parS sequence (73,76). Normally, such parS elements are located adjacent to the genes coding for the ParA and ParB proteins (35).…”

mentioning

confidence: 99%

Rational Design of an Artificial Genetic Switch: Co-Option of the H-NS-Repressed proU Operon by the VirB Virulence Master Regulator

Kane

Dorman

2011

J Bacteriol

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The H-NS protein represses the transcription of hundreds of genes in Gram-negative bacteria. Derepression is achieved by a multitude of mechanisms, many of which involve the binding of a protein to DNA at the repressed promoter in a manner that compromises the maintenance of the H-NS-DNA nucleoprotein repression complex. The principal virulence gene promoters in Shigella flexneri, the cause of bacillary dysentery, are repressed by H-NS. VirB, a protein that closely resembles members of the ParB family of plasmid-partitioning proteins, derepresses the operons that encode the main structural components and the effector proteins of the S. flexneri type III secretion system. Bioinformatic analysis suggests that VirB has been co-opted into its current role as an H-NS antagonist in S. flexneri. To test this hypothesis, the potential for VirB to act as a positive regulator of proU, an operon that is repressed by H-NS, was assessed. Although VirB has no known relationship with the osmoregulated proU operon, it could relieve H-NS-mediated repression when the parS-like VirB binding site was placed appropriately upstream of the RpoD-dependent proU promoter. These results reveal the remarkable facility with which novel regulatory circuits can evolve, at least among those promoters that are repressed by H-NS.

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“…Bacterial cells also contain the ParA family of ATPases that comprise a cytoskeletal element (Gerdes et al 2004;Leonard et al 2005;Hayes and Barilla 2006). ParA proteins are required for plasmid and chromosomal DNA segregation in many bacteria and have recently been shown to assemble polymers both in vivo and in vitro (Barilla et al 2005;Lim et al 2005;Adachi et al 2006;Ebersbach et al 2006;Fogel and Waldor 2006;Bouet et al 2007).…”

mentioning

confidence: 99%

Treadmilling of a prokaryotic tubulin-like protein, TubZ, required for plasmid stability in Bacillus thuringiensis

Larsen

Cusumano²,

Fujioka³

et al. 2007

Genes Dev.

178

218

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Prokaryotes rely on a distant tubulin homolog, FtsZ, for assembling the cytokinetic ring essential for cell division, but are otherwise generally thought to lack tubulin-like polymers that participate in processes such as DNA segregation. Here we characterize a protein (TubZ) from the Bacillus thuringiensis virulence plasmid pBtoxis, which is a member of the tubulin/FtsZ GTPase superfamily but is only distantly related to both FtsZ and tubulin. TubZ assembles dynamic, linear polymers that exhibit directional polymerization with plus and minus ends, movement by treadmilling, and a critical concentration for assembly. A point mutation (D269A) that alters a highly conserved catalytic residue within the T7 loop completely eliminates treadmilling and allows the formation of stable polymers at a much lower protein concentration than the wild-type protein.When expressed in trans, TubZ(D269A) coassembles with wild-type TubZ and significantly reduces the stability of pBtoxis, demonstrating a direct correlation between TubZ dynamics and plasmid maintenance. The tubZ gene is in an operon with tubR, which encodes a putative DNA-binding protein that regulates TubZ levels. Our results suggest that TubZ is representative of a novel class of prokaryotic cytoskeletal proteins important for plasmid stability that diverged long ago from the ancient tubulin/FtsZ ancestor.[Keywords: FtsZ; tubulin; cytoskeleton] Supplemental material is available at http://www.genesdev.org.

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Towards understanding the molecular basis of bacterial DNA segregation

Cited by 66 publications

References 134 publications

ParA2, aVibrio choleraechromosome partitioning protein, forms left-handed helical filaments on DNA

ParA2, aVibrio choleraechromosome partitioning protein, forms left-handed helical filaments on DNA

Rational Design of an Artificial Genetic Switch: Co-Option of the H-NS-Repressed proU Operon by the VirB Virulence Master Regulator

Treadmilling of a prokaryotic tubulin-like protein, TubZ, required for plasmid stability in Bacillus thuringiensis

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