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Chapter 34 : Regulation of Genes in Campylobacter jejuni
Category: Bacterial Pathogenesis
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Transcription factors are grouped on the basis of the presence of conserved motifs and their modes of DNA binding. Genome-wide analysis of several Campylobacter jejuni strains indicates that this species contains between approximately 1,650 and 1,800 genes. The C. jejuni genome carries only three sigma factors: RpoD, FliA, and RpoN; the remaining 34 regulators belong to the specific transcription factors. The main essential sigma factor regulating almost all C. jejuni promoters is RpoD. Genome-wide analysis of C. jejuni that is based on this sequence (TGGCAC-N5-TTGC) indicated the existence of 17 putative RpoN promoters. The 17 identified RpoN promoters of C. jejuni control the transcription of 23 genes, of which 15 encode proteins that are involved in the assembly of the flagella. The majority of MarR homologs are transcriptional repressors that are autoregulated. Comparative genomic analysis of C. jejuni revealed the existence of seven major plasticity regions (PR), three of which (PR4, PR5, and PR6) contain genes involved in the production and modification of antigenic surface structures. One mechanism of C. jejuni gene regulation may involve direct modulation of the function of the RNA polymerase. DNA-binding proteins dictate the correct regulation of gene expression, so that the optimal amount and type of proteins are produced in response to specific internal and external stimuli. Although considerable progress has been made, the knowledge of the mechanisms that control C. jejuni gene regulation is still fragmentary.
Key Concept Ranking
- Gene Expression and Regulation
DNA sequence logos to indicate the sequence conservation of the C. jejuni sigma factors RpoD (A), RpoN (B) and FliA (C). Sequence logos were made of 300 RpoD, 17 RpoN, and 10 FliA promoter sequences with the program Weblogo (http://www.bio.cam.ac.uk/seqlogo/logo.cgi). Sequence conservation is measured in bits, and the degree of conservation of the different nucleotides is indicated by the height of a stack of letters. Numbers under the nucleotides indicate the relative distance to the transcription start site.
Regulons belonging to the (A) FlgS/FlgR, (B) DccS/DccR, and (C) PhosS/PhosR two-component systems. The different two-component systems activate (+) or repress (–) the transcription of the indicated genes and operons. The sizes of the gene arrows correspond to the size of the genes.
Regulons belonging to Fur and PerR repressor proteins. The response regulators FurR and PerR repress (–) the transcription of the indicated genes and operons. Solid arrows point to genes for which binding of FurR to the promoter regions has been confirmed. Dashed arrows point to genes for direct binding of the transcription factor that still need to be demonstrated. The sizes of the gene arrows correspond to the size of the genes.
Regulons belonging to (A) NssR and (B) CmeR transcription factors. The different two-component systems activate (+) or repress (–) the transcription of the indicated genes and operons. The sizes of the gene arrows correspond to the size of the genes.
C. jejuni transcription factors