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  • 1
    Electronic Resource
    Electronic Resource
    A class of gyrB mutants, substantially unaffected in DNA topology, suppresses the Escherichia coli K12 fts Z84 mutation (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Previous work in our laboratory suggested that DNA topology could be implicated in the regulation of the division gene ftsZ. To settle this question, we have selected and characterized mutants in the gyrB gene able to phenotypically suppress the defects of the ftsZ84 mutation. No strict correlation was found between the degree of plasmid DNA relaxation and the level of suppression of the thermosensitivity of the ftsZ84 strain. Interestingly, the class of mutants that shows maximal suppression is substantially unaffected in DNA topology. In addition, the amount of ffsZ-specific mRNA in this class of mutants is comparable to that present in the ftsZ84 strain. These results hint that the ability of these gyrB mutants to correct the effects of the ftsZ84 mutation is largely unrelated to the function of the GyrB (as a part of DNA gyrase) in the control of DNA superhelicity and suggest hitherto unsuspected interaction between the ftsZ and gyrB gene products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb01878.x
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  • 2
    Electronic Resource
    Electronic Resource
    The expression of the DNA ligase gene of Escherichia coli is stimulated by relaxation of chromosomal supercoiling (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 3 (1989), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Many genes of Escherichia coli have been shown to be sensitive to DNA superhelicity. The superhelicity of the chromosome is itself also supercoiling-dependent. We have developed a general strategy for investigating how a particular gene responds to changes in DNA topology. This approach is used to study the E. coli ligase gene. The thermosensitivity of the E. coli ligts251 mutation can be phenotypically suppressed by mutations which map close to, or in, the gyrB gene and which affect the degree of DNA supercoillng. The level of suppression correlates with the degree of DNA relaxation observed, suggesting that the gene encoding the E. coli DNA ligase is activated by relaxation of the chromosomal DNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1989.tb00171.x
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  • 3
    Electronic Resource
    Electronic Resource
    A novel illegitimate recombination event: precise excision and reintegration with the Mu gem mutant prophage (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 13 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The bacteriophage Mu is known to insert its DNA more or less randomly within the Escherichia coli chromosome, as do transposable elements, but unlike the latter, precise excision of the prophage, thereby restoring the original sequence, is not observed with wild-type Mu, although it has been reported with certain defective mutants. We show here that the mutant prophage Mu gem2ts can excise precisely from at least three separate loci —malT, Iac and thyA (selected as Mal+, Lac+ and Thy+, respectively). This excision occurs under permissive conditions for phage development, is observed in fully immune (c+) lysogens, and is independent of RecA and of Mu transposase. Mu gemts2 excision is invariably accompanied by reintegration of a Mu gem2ts prophage elsewhere in the chromosome, in the case of Mal+ revertants, this prophage is systematically located at 94min on the E. coli chromosome. Mu gem2ts excision therefore sheds some light on the long-standing paradox of the lack of precise Mu excisio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00464.x
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  • 4
    Electronic Resource
    Electronic Resource
    FtsZ dimerization in vivo (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 32 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A hybrid assay, based on the properties of the λ repressor, was developed to detect FtsZ dimerization in Escherichia coli in vivo. A gene fusion comprising the N-terminal end of the λcI repressor gene and the complete E. coli ftsZ gene was constructed. The fused protein resulted in a functional λ repressor and was able to complement the thermosensitive mutant ftsZ84. Using the same strategy, a series of 10 novel mutants of FtsZ that are unable to dimerize was selected, and a deletion analysis of the protein was carried out. Characterization of these mutants allowed the identification of three separate FtsZ portions: the N-terminal of about 150 amino acids; the C-terminal of about 60 amino acids, which corresponds to the less conserved portion of the protein; and a central region of about 150 residues. Mutants belonging to this region would define the dimerization domain of FtsZ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01344.x
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  • 5
    Electronic Resource
    Electronic Resource
    The topoisomerase activity of T4 amG39 mutant is restored in Mu lysogens
    Amsterdam : Elsevier
    FEBS Letters 137 (1982), S. 49-52 
    Details
    ISSN: 0014-5793
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0014-5793(82)80312-8
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  • 6
    Electronic Resource
    Electronic Resource
    The mechanism of integration of phage Mu in the chromosome of Escherichia coli
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 88 (1979), S. 111-116 
    Details
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0006-291X(79)91703-0
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  • 7
    Electronic Resource
    Electronic Resource
    Reversal of Mu gem2ts-induced mutations (1995)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 17 (1995), S. 0 
    Details
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Mutations induced by the integration of a Mu gem2ts mutant prophage can revert at frequencies around 1 × 10−6, more than 104-fold higher than that obtained with Mu wild-type. Several aspects characterize Mu gem2ts precise excision: (i) the phage transposase is not involved; (ii) the RecA protein is not necessary; and (iii) revertants remain lysogenic with the prophage inserted elsewhere in the host genome. In addition, prophage re-integration seems to be non-randomly distributed, whereas Mu insertion into the host genome is a transposition event without any sequence specificity. In this paper, we describe that the site of re-integration somehow depends on the original site of insertion. Two alternative models are proposed to explain the strong correlation between donor and receptor sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6976.1995.tb00199.x
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  • 8
    Electronic Resource
    Electronic Resource
    Analysis of the killing effect of Mu ligts mutants on host cells (1987)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 40 (1987), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Infection of Escherichia coli with the mutant lig ts2 of bacteriophage Mu at a temperature nonpermissive for this mutant is lethal for the host cells. This effect is insensitive to phage immunity of the host cells, to inhibitors of protein synthesis and is not suppressed in trans in bacterial strains producing the Lig+ active protein. These data suggest that the killing effect of this mutant is different from the other kil functions identified in Mu [1].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1987.tb01992.x
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  • 9
    Electronic Resource
    Electronic Resource
    Mu gem3 as a tool to investigate the influence of chromosome supercoiling on gene expression in Escherichia coli K12 (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 66 (1990), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract We have developed a rapid method to investigate the influence of chromosome supercoiling on gene expressioni in Escherichia coli K12. This method exploits the ability of the gem3 mutant of the bacteriophage MU, even in the prophagic state in immune cells, to induce relaxation of the host chromosome. The experiments can thus be performed under physiological conditions, and without the use of the drugs. In theory, this method can be applied to any bacterial gene. Here we report the results obtained with four DNA replication and three cell division genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1990.tb03985.x
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  • 10
    Electronic Resource
    Electronic Resource
    Suppression of the thermosensitive DNA ligase mutations in Escherichia coli K12 through modulation of gene expression induced by phage Mu (1989)
    Springer
    Molecular genetics and genomics 216 (1989), S. 31-36 
    Details
    ISSN: 1617-4623
    Keywords: Mu lig ; DNA ligase ; DNA gyrase ; Gene expression ; DNA Topology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have previously shown that Mu can sustain the growth at non-permissive temperature of an Escherichia coli strain harbouring a thermosensitive mutation in the DNA ligase structural gene. This “complementation” reaches a maximal level with the Mu lig3 mutant which restores the viability of a ligts7 strain to the level of the wild type (Ghelardini et al. 1980; Paolozzi et al. 1980). In this study we analysed the characteristics of this phenotypic suppression in order to clarify its molecular mechanism. We found that an E. coli ligts7 strain lysogenic for the Mu lig3 mutant shows: (i) an increment in the host DNA ligase activity; (ii) an increase in the specific mRNA of the host lig gene; (iii) an increase (towards the relaxed state) in the average linking number of a resident plasmid; and (iv) a reduction in DNA gyrase activity. These results are compatible with the hypothesis that the Mu lig gene product by interfering with the host enzymatic apparatus controlling DNA topology leads to a reduction in chromosomal supercoiling. The relaxation of the chromosome could affect the transcription of the DNA ligase gene, amongst others. Thus, through this mechanism, the Mu lig gene product is able to modulate gene expression and hence suppress the effects of the E. coli ligts7 mutation. On the basis of the identification of this mechanism of action, we propose to change the name of the Mu lig gene (thought originally to be the structural gene for a bacteriophage ligase) to gem (gene expression modulation).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332227
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