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  • 1
    Electronic Resource
    Electronic Resource
    The datA locus predominantly contributes to the initiator titration mechanism in the control of replication initiation in Escherichia coli (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 44 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Replication of the Escherichia coli chromosome is initiated synchronously from all origins (oriC) present in a cell at a fixed time in the cell cycle under given steady state culture conditions. A mechanism to ensure the cyclic initiation events operates through the chromosomal site, datA, which titrates exceptionally large amounts of the bacterial initiator protein, DnaA, to prevent overinitiation. Deletion of the datA locus results in extra initiations and altered temporal control of replication. There are many other sites on the E. coli chromosome that can bind DnaA protein, but the contribution of these sites to the control of replication initiation has not been investigated. In the present study, seven major DnaA binding sites other than datA have been examined for their influence on the timing of replication initiation. Disruption of these seven major binding sites, either individually or together, had no effect on the timing of initiation of replication. Thus, datA seems to be a unique site that adjusts the balance between free and bound DnaA to ensure that there is only a single initiation event in each bacterial cell cycle. Mutation either in the second or the third DnaA box (a 9 basepair DnaA-binding sequence) in datA was enough to induce asynchronous and extra initiations of replication to a similar extent as that observed with the datA-deleted strain. These DnaA boxes may act as cores for the cooperative binding of DnaA to the entire datA region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02969.x
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  • 2
    Electronic Resource
    Electronic Resource
    Subcellular localization of Dna-initiation proteins of Bacillus subtilis: evidence that chromosome replication begins at either edge of the nucleoids (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 36 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We examined the intracellular distribution of Bacillus subtilis Dna-initiation proteins by immunofluorescence microscopy to visualize the initiation complex of replication in vivo. DnaA was distributed throughout the cytoplasm, but both DnaB and DnaI were always detected as foci during the cell-division cycle. Interaction of DnaI with the DnaC helicase by the yeast two-hybrid assay suggests that DnaI acts as a helicase loader. The number of DnaB and DnaI foci within the cell exceeded that of oriC. Although the foci were not always co-localized with oriC, they seemed to be localized near the outer or inner edges of the nucleoids at initiation of replication. When the replication cycle was synchronized in cells using a temperature-sensitive dnaA mutant, duplication of the oriC region was observed predominantly near an edge of the nucleoid. Before initiation occurred, each one of the DnaB and DnaI foci was frequently observed near there. Furthermore, DnaX–GFP (DnaX is a component of DNA polymerase III) foci were detected near either of the edges of the nucleoids at the onset of replication. These results suggest that the replisome is recruited into oriC near either edge of the nucleoids to initiate chromosome replication in B. subtilis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.01928.x
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  • 3
    Electronic Resource
    Electronic Resource
    Discovery of two novel families of proteins that are proposed to interact with prokaryotic SMC proteins, and characterization of the Bacillus subtilis family members ScpA and ScpB (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 45 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Structural maintenance of chromosomes (SMC) proteins are present in all eukaryotes and in many prokaryotes. Eukaryotic SMC proteins form complexes with various non-SMC subunits, which affect their function, whereas the prokaryotic homologues had no known non-SMC partners and were thought to act as simple homodimers. Here we describe two novel families of proteins, widespread in archaea and (Gram-positive) bacteria, which we denote ‘segregation and condensation proteins’ (Scps). ScpA genes are localized next to smc genes in nearly all SMC- containing archaea, suggesting that they belong to the same operon and are thus involved in a common process in the cell. The function of ScpA was studied in Bacillus subtilis, which also harbours a well characterized smc gene. Here we show that scpA mutants display characteristic phenotypes nearly identical to those of smc mutants, including temperature- sensitive growth, production of anucleate cells, formation of aberrant nucleoids, and chromosome splitting by the so-called guillotine effect. Thus, both SMC and ScpA are required for chromosome segregation and condensation. Interestingly, mutants of another B. subtilis gene, scpB, which is localized downstream from scpA, display the same phenotypes, which indicate that ScpB is also involved in these functions. ScpB is generally present in species that also encode ScpA. The physical interaction of ScpA and SMC was proven (i) by the use of the yeast two-hybrid system and (ii) by the isolation of a complex containing both proteins from cell extracts of B. subtilis. By extension, we speculate that interaction of orthologues of the two proteins is important for chromosome segregation in many archaea and bacteria, and propose that SMC proteins generally have non-SMC protein partners that affect their function not only in eukaryotes but also in prokaryotes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03012.x
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  • 4
    Electronic Resource
    Electronic Resource
    Deficiency of essential GTP-binding protein ObgE in Escherichia coli inhibits chromosome partition (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 41 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: GTP-binding proteins are involved in cell proliferation, development, signal transduction, protein elongation, etc. and construct the GTPase superfamily, whose structures and sequence motifs (G-1 to G-5) are highly conserved from prokaryote to eukaryote. Obg of Bacillus subtilis and Obg homologues of other bacteria belong to the GTPase superfamily and have been suggested as being essential for cell growth, development and monitoring of intracellular levels of GTP. We identified the Obg homologue in Escherichia coli, a protein previously known as YhbZ, which we have renamed ObgE. Double cross-over experiments showed that the obgE gene is essential for growth in E. coli. From characterization of the obgE temperature-sensitive mutant, we found that DNA replication was not inhibited, that the nucleoids did not partition and instead remained in the middle of cell, and that the cells elongated. Overproduction of ObgE also resulted in aberrant chromosome segregation. These data suggested that ObgE is involved directly or indirectly in E. coli chromosome partitioning. Characterization studies showed that ObgE is abundant in normal cells, partially associated with the membrane and does not associate with ribosomes such as in Obg of B. subtilis. We purified ObgE protein from a cell extract of E. coli, and the purified ObgE had GTPase activity and DNA-binding ability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02574.x
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  • 5
    Electronic Resource
    Electronic Resource
    A Bacillus subtilis gene-encoding protein homologous to eukaryotic SMC motor protein is necessary for chromosome partition (1998)
    Oxford BSL : Blackwell Science Ltd, UK
    Molecular microbiology 29 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have analysed the function of a gene of Bacillus subtilis, the product of which shows significant homology with eukaryotic SMC proteins essential for chromosome condensation and segregation. Two mutant strains were constructed; in one, the expression was under the control of the inducible spac promoter (conditional null) and, in the other, the gene was disrupted by insertion (disrupted null). Both could form colonies at 23°C but not at 37°C in the absence of the expression of the Smc protein, indicating that the B. subtilis smc gene was essential for cell growth at higher temperatures. Microscopic examination revealed the formation of anucleate and elongated cells and diffusion of nucleoids within the elongated cells in the disrupted null mutant grown at 23°C and in the conditional null mutant grown in low concentrations of IPTG at 37°C. In addition, immunofluorescence microscopy showed that subcellular localization of the Spo0J partition protein was irregular in the smc disrupted null mutant, compared with bipolar localization in wild-type cells. These results indicate that the B. subtilis smc gene is essential for chromosome partition. The role of B. subtilis Smc protein in chromosome partition is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00919.x
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  • 6
    Electronic Resource
    Electronic Resource
    ClpC regulates the fate of a sporulation initiation sigma factor, σH protein, in Bacillus subtilis at elevated temperatures (1998)
    Oxford BSL : Blackwell Science Ltd, UK
    Molecular microbiology 29 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Using a strain carrying a clpC–bgaB transcriptional fusion at the amyE locus, we found that the expression of a clpC operon was induced at the end of exponential growth in a σB-independent manner and ceased around T3.5 in the wild type but not in a spo0H mutant. This suggests that some gene product(s) whose expression is dependent on σH function is required for the turn-off of clpC transcription during an early stage of sporulation. A clpC deletion mutant showed a temperature-sensitive sporulation phenotype and exhibited an abnormally large accumulation of σH in the cell at 45°C after T2, at which time the σH level in the wild type had begun to decrease. These results, together with the fact that spo0H transcription in the clpC deletion mutant was similar to that of the wild type, suggested that ClpC may be responsible for the degradation of σH after the accomplishment of its role in sporulation. Moreover, as expected from these results, overproduction of Spo0A was also observed after the initiation of sporulation in the clpC deletion mutant at 45°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00943.x
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  • 7
    Electronic Resource
    Electronic Resource
    Subcellular localization of the Bacillus subtilis structural maintenance of chromosomes (SMC) protein (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 46 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Bacillus subtilis structural maintenance of chromosomes (SMC) protein is a member of a large family of proteins involved in chromosome organization. We found that SMC is a moderately abundant protein (∼1000 dimers per cell). In vivo cross-linking and immunoprecipitation assays revealed that SMC binds to many regions on the chromosome. Visualization of SMC in live cells using a fusion to the green fluorescent protein (GFP) and in fixed cells using immunofluorescence microscopy indicated that a portion of SMC localizes as discrete foci in positions similar to that of the DNA replication machinery (replisome). When visualized simultaneously, SMC and the replisome were often in similar regions of the cell but did not always co-localize. Persistence of SMC foci did not depend on ongoing replication, but did depend on ScpA and ScpB, two proteins thought to interact with SMC. Our results indicate that SMC is bound to many sites on the chromosome and a concentration of SMC is localized near replication forks, perhaps there to bind and organize newly replicated DNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03235.x
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  • 8
    Electronic Resource
    Electronic Resource
    Identification of a protein, YneA, responsible for cell division suppression during the SOS response in Bacillus subtilis (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 47 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A knock-out mutant of the dinR gene that encodes the SOS regulon repressor in Bacillus subtilis was constructed. The yneA, yneB and ynzC genes transcribed divergently from the dinR gene were strongly induced in mutant cells. Northern hybridization analyses revealed that these genes collectively form an operon and belong to the SOS regulon. The simultaneous deletion of dinR and yneA suppressed the filamentous phenotype of the dinR mutant. Furthermore, although yneA is suppressed in the wild-type cell in the absence of SOS induction, artificial expression of the YneA protein using an IPTG-inducible promoter resulted in cell elongation. Disruption of yneA significantly reduced cell elongation after the induction of the SOS response by mitomycin C in dinR+ cells. These results indicate that the YneA protein is responsible for cell division suppression during the SOS response in B. subtilis. Localization of the FtsZ protein to the cell division site was reduced in dinR-disrupted or yneA-expressing cells, further suggesting that the YneA protein suppresses cell division through the suppression of FtsZ ring formation. Interestingly, the B. subtilis YneA protein is structurally and phylogenetically unrelated to its functional counterpart in Escherichia coli, SulA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03360.x
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  • 9
    Electronic Resource
    Electronic Resource
    Two separate DNA sequences within oriC participate in accurate chromosome segregation in Bacillus subtilis (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 45 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Current views of bacterial chromosome segregation vary in respect of the likely presence or absence of an active segregation mechanism involving a mitotic-like apparatus. Furthermore, little is known about cis-acting elements for chromosome segregation in bacteria. In this report, we show that two separate DNA regions, a 3′ coding region of dnaA and the AT-rich sequence between dnaA and dnaN (the initial opening site of duplex DNA during replication), are necessary for efficient segregation of the chromosome in Bacillus subtilis. When a plasmid replicon was integrated into argG, far from oriC, on the chromosome and then the oriC function was disrupted, the oriC-deleted mutant formed anucleate cells at 5% possibly because of defects in chromosome segregation. However, when the two DNA sequences were added near oriN, frequency of anucleate cells decreased to 1%. In these cells, the origin (argG) regions were localized near cell poles, whereas they were randomly distributed in cells without the two DNA sequences. These results suggest that the two DNA sequences in and downstream of the dnaA gene participate in correct positioning of the replication origin region within the cell and that this function is associated with accurate chromosome segregation in B. subtilis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03016.x
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  • 10
    Electronic Resource
    Electronic Resource
    The BceRS two-component regulatory system induces expression of the bacitracin transporter, BceAB, in Bacillus subtilis (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 49 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: BceA and bceB encode a nucleotide-binding domain (NBD) and membrane-spanning domain (MSD) subunit, respectively, of an ATP-binding cassette (ABC) transporter in Bacillus subtilis. Disruption of these genes resulted in hypersensitivity to bacitracin, a peptide antibiotic that is non-ribosomally synthesized in some strains of Bacillus. Northern hybridization analyses showed that expression of the bceAB operon is induced by bacitracin present in the growth medium. The bceRS genes encoding a two-component regulatory system are located immediately upstream of bceAB. Deletion analyses of the bceAB promoter together with DNase I footprinting experiments revealed that a sensor kinase, BceS, responds to extracellular bacitracin either directly or indirectly and transmits a signal to a cognate response regulator, BceR. The regulator binds directly to the upstream region of the bceAB promoter and upregulates the expression of bceAB genes. The bcrC gene product is additionally involved in bacitracin resistance. The expression of bcrC is dependent on the ECF σ factors, σM and σX, but not on the BceRS two-component system. In view of these results, possible roles of BceA, BceB and BcrC in bacitracin resistance of B. subtilis 168 are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03653.x
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