1,721,072 research outputs found
Differential response of the bvg virulence regulon of Bordetella pertussis to MgSO4 modulation
No full textMagnesium sulfate is known to repress the expression of the virulence factors of Bordetella pertussis that are coordinately regulated by the bvg locus. We have tested the time required by MgSO4 to repress the synthesis of several bvg-regulated mRNA species and found that the promoters of the virulence genes (pertussis toxin, adenylate cyclase, and filamentous hemagglutinin) are repressed in 6 min, while the autogenously regulated promoters of the bvg locus (P1, P3, and P4) are repressed only several hours later. These data show a differential behavior between regulated and autoregulated genes of the bvg regulon
The DNA polymerase-encoding gene of Bacillus subtilis bacteriophage SPO1
No full textThe bacteriophage SPO1 DNA polymerase-encoding gene, which contains a self-splicing intron, has been sequenced and its amino acid (aa) sequence has been deduced. The aa sequence of SPO1 DNA polymerase shows a high degree of similarity with that of DNA polymerase I from Escherichia coli (PolI). Alignment with the sequences of Poll, and the φ29 and SPO1 DNA polymerases indicate that the aa residues that have been implicated in 3'→5' exonuclease activities are conserved. © 1992
Motility of Helicobacter priori is coordinately regulated by the transcriptional activator FlgR, an NtrC homolog
No full textσ54 is the subunit of bacterial RNA polymerase that transcribes from promoters with enhancer elements bound by enhancer-binding proteins. By computer searches of Helicobacter pylori genomic sequences, chromosomal gene disruption, and RNA analyses, we have identified σ54-recognized promoters that regulate transcription of flagellar basal body and hook genes, as well as the enhancer-binding protein FlgR (flagellum regulator), a transactivating protein of the NtrC family. We demonstrate that FlgR is required for bacterial motility and transcription of five promoters for seven basal body and hook genes. In addition, FlgR acts as a repressor of transcription of the σ28-regulated flaA flagellin gene promoter, while changes in DNA topology repress transcription of the σ54-regulated flaB flagellin gene promoter. Our data indicate that regulation of flagellar gene expression in H. priori shows similarities with that in enterobacteriaceae and Caulobacter
The autoregulatory HspR repressor protein governs chaperone gene transcription in Helicobacter pylori
No full textIn the present study, we provide evidence that the groESL, hrcA-grpE-dnaK and cbpA-hspR-orf operons encoding the major chaperones of the human gastric pathogen Helicobacter pylori are transcribed by the vegetative sigma factor σ80 and are regulated negatively by the transcriptional repressor HspR. In vitro studies with purified recombinant HspR protein established that the protein represses transcription by binding to large DNA regions centred around the transcription initiation site in the case of the P(cbp) promoter, and around -85 and -120 in the case of the P(gro) and P(hrc) promoters respectively. All three binding sites contain DNA motifs with some similarity to the HAIR sequence identified as a consensus for the HspR protein of Streptomyces. In contrast to the situation in Streptomyces, in which transcription of HspR-regulated genes is induced in response to heat shock, transcription of the HspR-dependent genes in H. pylori is not inducible by thermal stimuli. Transcription of the groESL and cbpA-hspR-orf operons is induced by osmotic shock, while transcription of the hrcA-grpE-dnaK operon, although HspR dependent, is not affected by salt treatment. The possibility that HspR could constitute a global transcriptional regulator for diverse cellular functions with implications for pathogenesis is discussed
Sequence of the bacteriophage SP01 gene 30
No full textThe bacteriophage SP01 gene 30, whose function is essential for DNA synthesis, has been analyzed for its primary structural features. Conditionally lethal mutations in the gene 30 locus have been mapped and sequenced, and the wild-type amino acid (aa) sequence has been deduced along with that of a co-transcribed and possibly co-translated upstream unidentified reading frame (URF). The aa sequence deduced for gene 30 shares partial similarity with protein P of bacteriophage λ, which participated in λ DNA replication, and also with the exonuclease, gp46, of bacteriophage T4. A lysine-rich region of the hypothetical product of the URF shares similarity with both the T4 DNA topoisomerase and the θ29 gene 3-encoded protein; the latter codes for a terminal protein which participates in the priming of DNA elongation. © 1992
DNA topology affects transcriptional regulation of the pertussis toxin gene of Bordetella pertussis in Escherichia coli and in vitro
No full textThe bvg locus of Bordetella pertussis encodes an environmentally inducible operon essential for the expression of virulence genes. We show that in Escherichia coli, the P(TOX) promoter cloned in cis of the bvg locus is activated and environmentally regulated. Cotransformation of E. coli with the bvg locus cloned in a low-copy-number plasmid and with the P(TOX) promoter cloned in a high-copy-number plasmid can give rise to two different results. If the P(TOX) promoter is cloned in the pGem-3 vector, transcription is absent. If the P(TOX) promoter is cloned in the plasmid pKK232, containing the P(TOX) promoter between two ribosomal gene terminators of transcription, transcription occurs, although regulation of transcription is abolished. Under these conditions, the intracellular amount of RNA transcripts is increased by adding to the culture medium novobiocin, an inhibitor of bacterial gyrases. In vitro, the transcription of the P(TOX) promoter is activated on E. coli RNA polymerase supplemented with cell extracts from wild-type B. pertussis. Addition of DNA gyrase to the mixture dramatically reduces the amount of RNA synthesized. Our data show that the products of the bvg locus, BvgA and BvgS, are directly involved in the regulation of the P(TOX) promoter in E. coli and that DNA topology may play a role in the induction of transcription
Targeting of Regulators as a Promising Approach in the Search for Novel Antimicrobial Agents
Full text linkSince the discovery of penicillin in the first half of the last century, antibiotics have become the pillars of modern medicine for fighting bacterial infections. However, pathogens resistant to antibiotic treatment have increased in recent decades, and efforts to discover new antibiotics have decreased. As a result, it is becoming increasingly difficult to treat bacterial infections successfully, and we look forward to more significant efforts from both governments and the scientific community to research new antibacterial drugs. This perspective article highlights the high potential of bacterial transcriptional and posttranscriptional regulators as targets for developing new drugs. We highlight some recent advances in the search for new compounds that inhibit their biological activity and, as such, appear very promising for treating bacterial infections
THE REGULATION OF THE PERTUSSIS TOXIN GENE OF BORDETELLA-PERTUSSIS IN ESCHERICHIA-COLI AND IN-VITRO IS SENSITIVE TO DNA TOPOLOGY
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The pertussis toxin liberation genes of Bordetella pertussis are transcriptionally linked to the pertussis toxin operon
No full textThe DNA sequence of the pertussis toxin operon (ptx) of Bordetella pertussis predicts that transcription of the operon ends downstream from the ptxS3 gene at a possible stem-loop structure. Secretion of the assembled pertussis toxin into the culture medium requires the expression of 8 genes arranged in an operon (ptl) and lying 55 bp downstream from the ptx operon. We have investigated the rule of this 55-bp intergenic region in transcriptional regulation of the ptl operon. Our results show that ptx transcripts transverse this DNA region and that the ptx and ptl operons are cotranscribed and coregulated by the P(TOX) promoter. Deletion of the 55-bp DNA region caused an increase in the amount of the ptl transcripts. It is likely that this DNA region is involved in regulation of the ptx-ptl expression
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