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  • 1
    Electronic Resource
    Electronic Resource
    Regulated transcription of Clostridium difficile toxin genes (1998)
    Oxford BSL : Blackwell Publishing Ltd
    Molecular microbiology 27 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Clostridium difficile toxA and toxB genes, encoding cytotoxic and enterotoxic proteins responsible for antibiotic-associated colitis and pseudomembranous colitis, were shown to be transcribed both from gene-specific promoters and from promoters of upstream genes. However, the gene-specific transcripts represented the majority of tox gene mRNAs. The 5′ ends of these mRNAs were shown to correspond to DNA sequences that had promoter activity when fused to the Escherichia coliβ-glucuronidase (gusA) gene and introduced into C. perfringens. The appearance of tox mRNA in C. difficile was repressed during exponential growth phase but increased substantially as cells entered stationary phase. When glucose or other rapidly metabolizable sugars were present in the medium, the stationary phase-associated induction was inhibited, indicating that the toxin genes are subject to a form of catabolite repression. This glucose effect was general to many toxinogenic strains having varying levels of toxin production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00663.x
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  • 2
    Electronic Resource
    Electronic Resource
    Transcription activation of a UV-inducible Clostridium perfringens bacteriocin gene by a novel σ factor (2005)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 55 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Expression of the plasmid-encoded Clostridium perfringens gene for bacteriocin BCN5 was shown to depend in vivo and in vitro on the activity of UviA protein. UviA,  also  plasmid-encoded,  proved  to  be an RNA polymerase σ factor and was also partly autoregulatory. The uviA gene has two promoters; one provided a UviA-independent, basal level of gene expression while the stronger, UviA-dependent promoter was only utilized after the cell experienced DNA damage. As a result, BCN5 synthesis is induced by treatment with UV light or mitomycin C. UviA is related to a special class of σ factors found to date only in Clostridium species and responsible for activating transcription of toxin genes in Clostridium difficile, Clostridium tetani, and Clostridium botulinum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04456.x
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  • 3
    Electronic Resource
    Electronic Resource
    Bacillus subtilis ilvB operon: an intersection of global regulons (2005)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 56 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The genes of the major Bacillus subtilis operon (ilvB) for biosynthesis of branched-chain amino acids are subject to multiple mechanisms of regulation. The global regulatory proteins CodY and TnrA bind upstream of the transcription start site and are likely to control transcription initiation, leucine-specific tRNA regulates transcriptional elongation, and unknown factors differentially cleave the full-length mRNA. Another global regulator, CcpA, known to be required for ilvB transcription, was shown here to act directly at the ilvB promoter by a novel mechanism. Although CcpA was able to bind to the ilvB promoter region, it stimulated transcription significantly only when CodY was present, suggesting that CcpA acts primarily by interfering with repression by CodY. Additionally, CcpA was shown to control indirectly the expression of other CodY-regulated target genes, apparently by altering the intracellular level of branched-chain amino acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04634.x
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  • 4
    Electronic Resource
    Electronic Resource
    Activation of the Bacillus subtilis global regulator CodY by direct interaction with branched-chain amino acids (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 53 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: CodY, a GTP-activated global transcriptional regulator of early stationary phase genes, is conserved in many Gram-positive bacterial species. Recently, a number of novel targets regulated by CodY have been identified, including three Bacillus subtilis operons involved in branched-chain amino acid (BCAA) biosynthesis (Molle, V., et al., 2003, J Bacteriol 185: 1911–1922). The mechanism of involvement of CodY in regulating the ilvB operon was investigated here using in vivo transcriptional fusions, in vitro gel mobility shift assays and DNase I footprinting assays. CodY was found to mediate regulation of the ilvB operon by GTP and BCAAs and to bind to the ilvB promoter region. BCAAs increased the affinity of CodY for the ilvB promoter and for all other CodY targets tested. This effect of BCAAs in vitro was additive with the effect of GTP on CodY DNA-binding activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04135.x
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  • 5
    Electronic Resource
    Electronic Resource
    Regulation of the Bacillus subtilis ccpC gene by CcpA and CcpC (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 43 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Bacillus subtilis CcpC, a LysR-type transcriptional regulator, represses the transcription of genes for citrate synthase (citZ) and aconitase (citB) in response to citrate availability. Transcription of ccpC was shown to initiate at two promoters, P1, located just upstream of the ccpC gene, and P2, located within or upstream of the neighbouring ykuL gene. Expression from the ccpC-specific promoter (P1) was negatively regulated by CcpC but independent of the carbon source in the medium. Gel shift and DNase I footprinting experiments revealed that CcpC binds to an interrupted dyad sequence that surrounds the ccpC transcriptional start point. Transcription of ccpC from the upstream promoter (P2) was repressed by glucose in a CcpA-dependent manner. A putative CcpA binding site (cre) was identified upstream of the –35 region of the P1 promoter. Transcriptional fusion studies demonstrated that glucose repression of ccpC expression from the P2 promoter depends on this cre site. In addition, DNase I footprinting experiments showed that CcpA specifically binds to this cre site and that the introduction of mutations (cre*) into this site abolished the binding. These results suggest that CcpA may control CcpC syn-thesis by acting as a road-block to readthrough transcription from the P2 promoter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02751.x
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  • 6
    Electronic Resource
    Electronic Resource
    GabR, a member of a novel protein family, regulates the utilization of γ-aminobutyrate 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: The Bacillus subtilis ycnG (gabT) and ycnH (gabD) genes were shown to encode γ-aminobutyrate (GABA) aminotransferase and succinic semi-aldehyde dehydrogenase, respectively, and to form a GABA-inducible operon. Null mutations in gabT, gabD or the divergently transcribed ycnF (gabR) gene blocked the utilization of GABA as sole nitrogen source. GabR proved to be a transcriptional activator of the gabTD operon and a negative autoregulator. The target of GabR action was localized to an 87 bp region that includes both gabR and gabT promoters. GabR is a member of a novel but widespread family of chimeric bacterial proteins that have apparent DNA-binding and aminotransferase domains. Mutations in conserved residues of the putative aminotransferase domain abolished GabR function as a transcriptional activator, but did not affect its activity as a negative autoregulator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03036.x
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  • 7
    Electronic Resource
    Electronic Resource
    Efficient sporulation in Clostridium difficile requires disruption of the σK gene (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 48 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A 14.6 kb prophage-like insertion, termed skinCd, was found to interrupt the sigK gene, which encodes an RNA polymerase sigma factor essential for sporulation, in six strains of Clostridium difficile. Until now, Bacillus subtilis was the only spore-former shown to carry such an insertion, and the presence of the insertion is not required for efficient sporulation in this organism. The B. subtilis and C. difficile skin elements proved to be divergent in sequence, inserted at different sites within the sigK gene and in opposite orientations. The skinCd element was excised from the chromosome specifically during sporulation, forming a circular molecule. Two natural isolates of C. difficile lacked the skinCd element and were defective in sporulation. When a merodiploid strain was created that carries both interrupted and uninterrupted versions of the sigK gene, the cells became Spo–, showing that the uninterrupted gene is dominant and inhibits sporulation. C. difficile sigK genes, whether skinCd+ or skinCd–, lack the N-terminal pro-sequence found in all other sigK genes studied to date. Thus, regulated excision of skinCd appears to be a critical mechanism for achieving proper temporal activation of σK.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03471.x
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  • 8
    Electronic Resource
    Electronic Resource
    Direct and indirect roles of CcpA in regulation of Bacillus subtilis Krebs cycle genes (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: Carbon catabolite repression of the Bacillus subtilis citrate synthase (citZ) and aconitase (citB) genes, previously known to be regulated by CcpC, was shown to depend on CcpA as well. Transcription of the citZ gene was partially derepressed in ccpA and ccpC single mutants and fully derepressed in a ccpA ccpC double mutant. DNase I footprinting studies showed that CcpA binds to a catabolite-responsive element (cre) site located at positions +80 to +97 with respect to the transcription start site, whereas CcpC binds at positions −14 to +6 and +16 to +36. Mutations in the citZ cre site greatly altered CcpA binding and repression. A ccpA null mutation also caused partial derepression of citB. Disruption of citrate synthase activity, however, suppressed the effect of the ccpA mutation, suggesting that increased citrate accumulation in a ccpA mutant partially inactivates CcpC and causes partial derepression of citB. Therefore, CcpA controls expression of Krebs cycle genes directly by regulating transcription of citZ and in-directly by regulating availability of citrate, the inducer for CcpC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03003.x
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  • 9
    Electronic Resource
    Electronic Resource
    Interaction of Cody, a novel Bacillus subtillis DNA-binding protein, with the dpp promoter region (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 20 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The product of the codY gene is required for nutritional repression of the Bacillus subtilis dipeptide permease operon (dpp), an operon expressed at early stationary phase in nutrient-rich medium. Though unrelated to any known DNA-binding protein, Cody was shown to bind specifically to the dpp promoter region. DNase I footprinting experiments revealed that the Cody-protected region encompasses the dpp transcription start site and overlaps with the region protected by another regulatory protein, AbrB. Cody and AbrB were found to compete, in vitro, for binding to the dpp promoter region. Binding of Cody was altered in mutants defective in nutritional regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1996.tb02522.x
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  • 10
    Electronic Resource
    Electronic Resource
    A gene required for nutritional repression of the Bacillus subtilis dipeptide permease operon (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 15 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: An insertion mutation was isolated that resulted in derepressed expression of the Bacillus subtilis dipeptide transport operon (dpp) during the exponential growth phase in rich medium. DNA flanking the site of insertion was found to encode an operon (codVWXY) of four potential open reading frames (ORFs). The deduced product of the codV ORF is similar to members of the λ Int family; CodW and CodX are homologous to HsIV and HsIU, two putative heat-shock proteins from Escherichia coli, and to LapC and LapA, two gene products of unknown function from Pasteurella haemolytica. CodX also shares homology with a family of ATPases, including CIpX, a regulatory subunit of the E. coli ClpP protease. CodY does not have any homologues in the databases. The insertion mutation and all previously isolated spontaneous cod mutations were found to map In codY. In-frame deletion mutations in each of the other cod genes revealed that only codY is required for repression of dpp in nutrient-rich medium. The cody mutations partially relieved amino acid repression of the histidine utilization (hut) operon but had no effect on regulation of certain other early stationary phase-induced genes, such as spoVG and gsiA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.tb02378.x
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