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Tn917 targets the region where DNA replication terminates in Bacillus subtilis, highlighting a difference in chromosome processing in the firmicutes. J Bacteriol 2009; 191:7623-7. [PMID: 19820088 DOI: 10.1128/jb.01023-09] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The bacterial transposon Tn917 inserts preferentially in the terminus region of some members of the Firmicutes. To determine what molecular process was being targeted by the element, we analyzed Tn917 target site selection in Bacillus subtilis. We find that Tn917 insertions accumulate around the central terminators, terI and terII, in wild-type cells with or without the SPbeta lysogen. Highly focused targeting around terI and terII requires the trans-acting termination protein RTP, but it is unaffected in strains compromised in dimer resolution or chromosome translocation. This work indicates that Tn917 is sensitive to differences in DNA replication termination between the Firmicutes.
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2
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Broco M, Marques A, Oliveira S, Rodrigues-Pousada C. Characterisation of the 11 Kb DNA region adjacent to the gene encodingDesulfovibrio gigasflavoredoxin. ACTA ACUST UNITED AC 2009; 16:207-16. [PMID: 16147877 DOI: 10.1080/10425170500088296] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Flavoredoxin is an FMN binding protein that functions as an electron carrier in the sulphate metabolism of Desulfovibrio gigas. The neighbouring DNA regions of the gene encoding flavoredoxin were sequenced and characterised. Transcript analysis of the flavoredoxin gene resulted in a positive band corresponding to the size of the coding region, suggesting that flavoredoxin is encoded by a monocystronic unit, as previously suggested by sequence analysis. Analysis of the adjacent DNA regions revealed several interesting genes. The sequenced DNA regions contain nine open reading frames (ORFs) organised in two polycystronic and two monocystronic units. These genes encode proteins involved in different metabolic pathways, namely in DNA methylation, tRNA and rRNA modification, mRNA metabolism, cell division, CoA synthesis and lipoprotein transport across the membrane.
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Affiliation(s)
- Manuela Broco
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida República (EAN), Oeiras, Portugal
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3
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Massey TH, Mercogliano CP, Yates J, Sherratt DJ, Löwe J. Double-stranded DNA translocation: structure and mechanism of hexameric FtsK. Mol Cell 2006; 23:457-69. [PMID: 16916635 DOI: 10.1016/j.molcel.2006.06.019] [Citation(s) in RCA: 190] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2005] [Revised: 05/15/2006] [Accepted: 06/13/2006] [Indexed: 11/21/2022]
Abstract
FtsK is a DNA translocase that coordinates chromosome segregation and cell division in bacteria. In addition to its role as activator of XerCD site-specific recombination, FtsK can translocate double-stranded DNA (dsDNA) rapidly and directionally and reverse direction. We present crystal structures of the FtsK motor domain monomer, showing that it has a RecA-like core, the FtsK hexamer, and also showing that it is a ring with a large central annulus and a dodecamer consisting of two hexamers, head to head. Electron microscopy (EM) demonstrates the DNA-dependent existence of hexamers in solution and shows that duplex DNA passes through the middle of each ring. Comparison of FtsK monomer structures from two different crystal forms highlights a conformational change that we propose is the structural basis for a rotary inchworm mechanism of DNA translocation.
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Affiliation(s)
- Thomas H Massey
- Division of Molecular Genetics, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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4
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Wang SCE, West L, Shapiro L. The bifunctional FtsK protein mediates chromosome partitioning and cell division in Caulobacter. J Bacteriol 2006; 188:1497-508. [PMID: 16452433 PMCID: PMC1367234 DOI: 10.1128/jb.188.4.1497-1508.2006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial chromosome partitioning and cell division are tightly connected cellular processes. We show here that the Caulobacter crescentus FtsK protein localizes to the division plane, where it mediates multiple functions involved in chromosome segregation and cytokinesis. The first 258 amino acids of the N terminus are necessary and sufficient for targeting the protein to the division plane. Furthermore, the FtsK N terminus is required to either assemble or maintain FtsZ rings at the division plane. The FtsK C terminus is essential in Caulobacter and is involved in maintaining accurate chromosome partitioning. In addition, the C-terminal region of FtsK is required for the localization of the topoisomerase IV ParC subunit to the replisome to facilitate chromosomal decatenation prior to cell division. These results suggest that the interdependence between chromosome partitioning and cell division in Caulobacter is mediated, in part, by the FtsK protein.
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Affiliation(s)
- Sherry C E Wang
- Department of Developmental Biology, Stanford University School of Medicine, Beckman Center, B300, 279 Campus Dr., Stanford, California 94304-5329, USA
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5
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Bigot S, Corre J, Louarn JM, Cornet F, Barre FX. FtsK activities in Xer recombination, DNA mobilization and cell division involve overlapping and separate domains of the protein. Mol Microbiol 2004; 54:876-86. [PMID: 15522074 DOI: 10.1111/j.1365-2958.2004.04335.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Escherichia coli FtsK is a multifunctional protein that couples cell division and chromosome segregation. Its N-terminal transmembrane domain (FtsK(N)) is essential for septum formation, whereas its C-terminal domain (FtsK(C)) is required for chromosome dimer resolution by XerCD-dif site-specific recombination. FtsK(C) is an ATP-dependent DNA translocase. In vitro and in vivo data point to a dual role for this domain in chromosome dimer resolution (i) to directly activate recombination by XerCD-dif and (ii) to bring recombination sites together and/or to clear DNA from the closing septum. FtsK(N) and FtsK(C) are separated by a long linker region (FtsK(L)) of unknown function that is highly divergent between bacterial species. Here, we analysed the in vivo effects of deletions of FtsK(L) and/or of FtsK(C), of swaps of these domains with their Haemophilus influenzae counterparts and of a point mutation that inactivates the walker A motif of FtsK(C). Phenotypic characterization of the mutants indicated a role for FtsK(L) in cell division. More importantly, even though Xer recombination activation and DNA mobilization both rely on the ATPase activity of FtsK(C), mutants were found that can perform only one or the other of these two functions, which allowed their separation in vivo for the first time.
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Affiliation(s)
- Sarah Bigot
- Laboratoire de Microbiologie et de Génétique moléculaire du CNRS, 118 route de Narbonne, 31062 Toulouse Cedex 4, France
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6
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Dohmann K, Strommenger B, Stevenson K, de Juan L, Stratmann J, Kapur V, Bull TJ, Gerlach GF. Characterization of genetic differences between Mycobacterium avium subsp. paratuberculosis type I and type II isolates. J Clin Microbiol 2004; 41:5215-23. [PMID: 14605167 PMCID: PMC262536 DOI: 10.1128/jcm.41.11.5215-5223.2003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A combination of representational difference analysis and comparative DNA sequencing revealed that four type I (sheep) isolates of Mycobacterium avium subsp. paratuberculosis were differentiated from nine type II (bovine) isolates by the presence of an 11-bp insertion in a novel M. avium subsp. paratuberculosis-specific region of genomic DNA. Further, our studies show that M. avium subsp. paratuberculosis type I isolates contain three type-specific loci that are missing in M. avium subsp. paratuberculosis type II but are present in M. avium subsp. avium. Taken together, the results are consistent with the hypothesis that M. avium subsp. paratuberculosis type I strains are an evolutionary intermediate between M. avium subsp. avium and M. avium subsp. paratuberculosis type II isolates or share a subset of M. avium subsp. avium type-specific loci through horizontal transfer.
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Affiliation(s)
- Karen Dohmann
- Department of Infectious Diseases, Institute for Microbiology, School of Veterinary Medicine Hannover, D-30173 Hannover, Germany
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7
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Goksör M, Diez A, Enger J, Hanstorp D, Nyström T. Analysis of molecular diffusion in ftsK cell-division mutants using laser surgery. EMBO Rep 2003; 4:867-71. [PMID: 12947413 PMCID: PMC1326354 DOI: 10.1038/sj.embor.embor916] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2003] [Revised: 07/10/2003] [Accepted: 07/10/2003] [Indexed: 11/10/2022] Open
Abstract
Escherichia coli cells that lack the carboxy-terminal part of FtsK fail to segregate their chromosomes properly during cytokinesis and tend to form chains. These chains are possibly formed as a result of DNA being trapped in the division planes or a failure to fuse the membrane during septum formation. If so, small molecules might diffuse between the apparent cell compartments. To investigate this theory, we developed an optical workstation that allows simultaneous imaging of and surgical operations on cellular objects in the sub-micrometre range. By surgical incisions of E. coli cell poles, diffusion of propidium iodide (PI) can be followed in real time. This analysis showed that PI was unable to diffuse from one cell equivalent to another in chain-forming ftsK mutants. Thus, the cytoplasm of the cell compartments in the chains seems to be fully separated.
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Affiliation(s)
- Mattias Goksör
- Department of Physics, Chalmers University of
Technology and Göteborg University, Fysikgränd 3,
SE-41296 Göteborg, Sweden
| | - Alfredo Diez
- Department of Cell and Molecular
Biology—Microbiology, Göteborg University, Box 462,
SE-405 30 Göteborg, Sweden
| | - Johan Enger
- Department of Physics, Chalmers University of
Technology and Göteborg University, Fysikgränd 3,
SE-41296 Göteborg, Sweden
| | - Dag Hanstorp
- Department of Physics, Chalmers University of
Technology and Göteborg University, Fysikgränd 3,
SE-41296 Göteborg, Sweden
| | - Thomas Nyström
- Department of Cell and Molecular
Biology—Microbiology, Göteborg University, Box 462,
SE-405 30 Göteborg, Sweden
- Tel: +46 31 773 2582; Fax: +46 31 773 2599;
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Kvint K, Nachin L, Diez A, Nyström T. The bacterial universal stress protein: function and regulation. Curr Opin Microbiol 2003; 6:140-5. [PMID: 12732303 DOI: 10.1016/s1369-5274(03)00025-0] [Citation(s) in RCA: 338] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The universal stress protein A (UspA) superfamily encompasses an ancient and conserved group of proteins that are found in bacteria, Archea, fungi, flies and plants. The Escherichia coli UspA is produced in response to a large number of different environmental onslaughts and UspA is one of the most abundant proteins in growth-arrested cells. Although insights into the regulation of the E. coli uspA gene have been gained, the exact roles of the Usp proteins and Usp domains remain enigmatic; they appear, in some cases, to be linked to resistance to DNA-damaging agents and to respiratory uncouplers.
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Affiliation(s)
- Kristian Kvint
- Department of Cell and Molecular Biology, Microbiology, Göteborg University, Medicinaregatan 9C, 413 90 Göteborg, Sweden
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Åkerlund T, Gullbrand B, Nordström K. Effects of the Min system on nucleoid segregation in Escherichia coli. MICROBIOLOGY (READING, ENGLAND) 2002; 148:3213-3222. [PMID: 12368455 DOI: 10.1099/00221287-148-10-3213] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Min system of Escherichia coli directs cell division to the mid-cell by a mechanism that involves the dynamic localization of all of its three constituent proteins, MinC, MinD and MinE. Both the Min system and the nucleoid regulate cell division negatively and strains of E. coli lacking a functional Min system can divide at nucleoid-free cell poles in addition to the nucleoid-free region between newly segregated nucleoids. Interestingly, E. coli strains with a defective Min system have disturbed nucleoid segregation and the cause for this disturbance is not known. It is reported here that growth conditions promoting a higher frequency of polar divisions also lead to a more pronounced disturbance in nucleoid segregation. In strains with an intact Min system, expression of MinE, but not of MinD, from an inducible promoter was followed by impaired nucleoid segregation. These results suggest that the disturbed nucleoid segregation in min mutants is not caused by polar divisions per se, nor by impaired resolution of chromosome dimers in min mutants, leaving open the possibility that the Min system has a direct effect on nucleoid segregation. It is also shown how the disturbed nucleoid segregation can explain in part the unexpected finding that the clear majority of cells in min mutant populations contain 2(n) (n=0, 1, 2.) origins of replication.
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Affiliation(s)
- Thomas Åkerlund
- Department of Bacteriology, Swedish Institute for Infectious Disease Control, 171 82, Solna, Sweden1
| | - Björn Gullbrand
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Box 596, S-751 24, Uppsala, Sweden2
| | - Kurt Nordström
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Box 596, S-751 24, Uppsala, Sweden2
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10
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Diez AA, Tunlid A, Nyström T. The Escherichia coli ftsK1 mutation attenuates the induction of sigma(S)-dependent genes upon transition to stationary phase. FEMS Microbiol Lett 2002; 206:19-23. [PMID: 11786251 DOI: 10.1111/j.1574-6968.2002.tb10980.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
A mutation in the cell division gene ftsK causes super-induction of sigma(70)-dependent stress defense genes, such as uspA, during entry of cells into stationary phase. In contrast, we report here that stationary phase induction of sigma(S)-dependent genes, uspB and cfa, is attenuated and that sigma(S) accumulates at a lower rate in ftsK1 cells. Ectopic overexpression of rpoS restored induction of the rpoS regulon in the ftsK mutant, as did a deletion in the recA gene. Thus, a mutation in the cell division gene, ftsK, uncouples the otherwise coordinated induction of sigma(S)-dependent genes and the universal stress response gene, uspA, during entry into stationary phase.
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Affiliation(s)
- Alfredo A Diez
- Department of Cell and Molecular Biology-Microbiology, Göteborg, Sweden
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11
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Gustavsson N, Diez A, Nyström T. The universal stress protein paralogues of Escherichia coli are co-ordinately regulated and co-operate in the defence against DNA damage. Mol Microbiol 2002; 43:107-17. [PMID: 11849540 DOI: 10.1046/j.1365-2958.2002.02720.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have cloned, characterized and inactivated genes encoding putative UspA paralogues in Escherichia coli. The yecG (uspC), yiiT (uspD) and ydaA (uspE) genes were demonstrated to encode protein pro-ducts and these were mapped to spots in the E. coli proteomic database. Expression analysis using chromosomal transcriptional lacZ fusions and two-dimensional gels revealed that all usp genes analysed are regulated in a similar fashion. Thus, uspC, D and E are all induced in stationary phase and by a variety of stresses causing growth arrest of cells. Induction is independent of rpoS but is abolished in a deltarelA deltaspoT (ppGpp0) background and rescued by suppressor mutations rendering the beta-subunit of RNA polymerase to behave like a stringent polymerase. Ectopic elevation of ppGpp levels in growing cells, by overproducing the RelA protein, triggered the induction of all usp genes. The expression of all usp genes was also elevated by a mutation in the ftsK cell division gene, and this super-induction could be suppressed by inactivating recA indicating that the usp paralogues are involved in the management of DNA. Indeed, uspC, uspD and uspE deletion mutants were all found to be sensitive to UV exposure. Overexpression of UspD could compensate for the lack of a chromosomal uspD gene but not a uspA gene. Similarly, UspA overproduction could only compensate for the lack of chromosomal uspA. Moreover, combination of usp mutations had no additive effect on UV sensitivity indicating that they are all co-operating and required in the same pathway, which could explain the co-ordinated regulation of the genes.
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Affiliation(s)
- N Gustavsson
- Department of Cell and Molecular Biology, Göteborg University, Box 462, SE-405 30 Göteborg, Sweden
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12
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Chen JC, Beckwith J. FtsQ, FtsL and FtsI require FtsK, but not FtsN, for co-localization with FtsZ during Escherichia coli cell division. Mol Microbiol 2001; 42:395-413. [PMID: 11703663 DOI: 10.1046/j.1365-2958.2001.02640.x] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During cell division in Gram-negative bacteria, the cell envelope invaginates and constricts at the septum, eventually severing the cell into two compartments, and separating the replicated genetic materials. In Escherichia coli, at least nine essential gene products participate directly in septum formation: FtsA, FtsI, FtsL, FtsK, FtsN, FtsQ, FtsW, FtsZ and ZipA. All nine proteins have been localized to the septal ring, an equatorial ring structure at the division site. We used translational fusions to green fluorescent protein (GFP) to demonstrate that FtsQ, FtsL and FtsI localize to potential division sites in filamentous cells depleted of FtsN, but not in those depleted of FtsK. We also constructed translational fusions of FtsZ, FtsA, FtsQ, FtsL and FtsI to enhanced cyan or yellow fluorescent protein (ECFP or EYFP respectively), GFP variants with different fluorescence spectra. Examination of cells expressing different combinations of the fusions indicated that FtsA, FtsQ, FtsL and FtsI co-localize with FtsZ in filaments depleted of FtsN. These localization results support the model that E. coli cell division proteins assemble sequentially as a multimeric complex at the division site: first FtsZ, then FtsA and ZipA independently of each other, followed successively by FtsK, FtsQ, FtsL, FtsW, FtsI and FtsN.
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Affiliation(s)
- J C Chen
- Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
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13
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McCool JD, Sandler SJ. Effects of mutations involving cell division, recombination, and chromosome dimer resolution on a priA2::kan mutant. Proc Natl Acad Sci U S A 2001; 98:8203-10. [PMID: 11459954 PMCID: PMC37422 DOI: 10.1073/pnas.121007698] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recombinational repair of replication forks can occur either to a crossover (XO) or noncrossover (non-XO) depending on Holliday junction resolution. Once the fork is repaired by recombination, PriA is important for restarting these forks in Escherichia coli. PriA mutants are Rec(-) and UV sensitive and have poor viability and 10-fold elevated basal levels of SOS expression. PriA sulB mutant cells and their nucleoids were studied by differential interference contrast and fluorescence microscopy of 4',6-diamidino-2-phenylindole-stained log phase cells. Two populations of cells were seen. Eighty four percent appeared like wild type, and 16% of the cells were filamented and had poorly partitioned chromosomes (Par(-)). To probe potential mechanisms leading to the two populations of cells, mutations were added to the priA sulB mutant. Mutating sulA or introducing lexA3 decreased, but did not eliminate filamentation or defects in partitioning. Mutating either recA or recB virtually eliminated the Par(-) phenotype. Filamentation in the recB mutant decreased to 3%, but increased to 28% in the recA mutant. The ability to resolve and/or branch migrate Holliday junctions also appeared crucial in the priA mutant because removing either recG or ruvC was lethal. Lastly, it was tested whether the ability to resolve chromosome dimers caused by XOs was important in a priA mutant by mutating dif and the C-terminal portion of ftsK. Mutation of dif showed no change in phenotype whereas ftsK1cat was lethal with priA2kan. A model is proposed where the PriA-independent pathway of replication restart functions at forks that have been repaired to non-XOs.
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Affiliation(s)
- J D McCool
- Department of Microbiology, University of Massachusetts, 203 Morrill Science Center IVN, Amherst, MA 01003, USA
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14
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Sciochetti SA, Piggot PJ, Blakely GW. Identification and characterization of the dif Site from Bacillus subtilis. J Bacteriol 2001; 183:1058-68. [PMID: 11208805 PMCID: PMC94974 DOI: 10.1128/jb.183.3.1058-1068.2001] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacteria with circular chromosomes have evolved systems that ensure multimeric chromosomes, formed by homologous recombination between sister chromosomes during DNA replication, are resolved to monomers prior to cell division. The chromosome dimer resolution process in Escherichia coli is mediated by two tyrosine family site-specific recombinases, XerC and XerD, and requires septal localization of the division protein FtsK. The Xer recombinases act near the terminus of chromosome replication at a site known as dif (Ecdif). In Bacillus subtilis the RipX and CodV site-specific recombinases have been implicated in an analogous reaction. We present here genetic and biochemical evidence that a 28-bp sequence of DNA (Bsdif), lying 6 degrees counterclockwise from the B. subtilis terminus of replication (172 degrees ), is the site at which RipX and CodV catalyze site-specific recombination reactions required for normal chromosome partitioning. Bsdif in vivo recombination did not require the B. subtilis FtsK homologues, SpoIIIE and YtpT. We also show that the presence or absence of the B. subtilis SPbeta-bacteriophage, and in particular its yopP gene product, appears to strongly modulate the extent of the partitioning defects seen in codV strains and, to a lesser extent, those seen in ripX and dif strains.
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Affiliation(s)
- S A Sciochetti
- Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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15
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Barre FX, Aroyo M, Colloms SD, Helfrich A, Cornet F, Sherratt DJ. FtsK functions in the processing of a Holliday junction intermediate during bacterial chromosome segregation. Genes Dev 2000; 14:2976-88. [PMID: 11114887 PMCID: PMC317095 DOI: 10.1101/gad.188700] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In bacteria with circular chromosomes, homologous recombination can generate chromosome dimers that cannot be segregated to daughter cells at cell division. Xer site-specific recombination at dif, a 28-bp site located in the replication terminus region of the chromosome, converts dimers to monomers through the sequential action of the XerC and XerD recombinases. Chromosome dimer resolution requires that dif is positioned correctly in the chromosome, and the activity of FtsK, a septum-located protein that coordinates cell division with chromosome segregation. Here, we show that cycles of XerC-mediated strand exchanges form and resolve Holliday junction intermediates back to substrate irrespective of whether conditions support a complete recombination reaction. The C-terminal domain of FtsK is sufficient to activate the exchange of the second pair of strands by XerD, allowing both intra- and intermolecular recombination reactions to go to completion. Proper positioning of dif in the chromosome and of FtsK at the septum is required to sense the multimeric state of newly replicated chromosomes and restrict complete Xer reactions to dimeric chromosomes.
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Affiliation(s)
- F X Barre
- Division of Molecular Genetics, Department of Biochemistry, University of Oxford, OX1 3QU, UK
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