Genes for tRNAArg Located in the Upstream Region of the Shiga Toxin II Operon in Enterohemorrhagic Escherichia coli O157:H7

Kanjo, Naoko; Inokuchi, Hachiro

doi:10.1093/dnares/6.1.71

Cited by 10 publications

(5 citation statements)

References 19 publications

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“…Phages 21, ST64T and PS3 also carry one or both of these tRNA sequences in this location, but these have not been previously recognized as tRNA genes 22,25,26 (and GenBank accession AJ011579). Some other lambdoid phages, including 933W, 27 VT2-Sa 28 and FP27 29 carry isoleucine and arginine tRNA genes in this position, but the role of such tRNA genes is unknown in these cases (also see the text and Figure S3 of the Supplementary Material).…”

Section: Resultsmentioning

confidence: 99%

The Chromosome of Shigella flexneri Bacteriophage Sf6: Complete Nucleotide Sequence, Genetic Mosaicism, and DNA Packaging

Casjens

Winn-Stapley

Gilcrease

et al. 2004

Journal of Molecular Biology

130

152

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Section: Resultsmentioning

confidence: 99%

The Chromosome of Shigella flexneri Bacteriophage Sf6: Complete Nucleotide Sequence, Genetic Mosaicism, and DNA Packaging

Casjens

Winn-Stapley

Gilcrease

et al. 2004

Journal of Molecular Biology

130

152

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“…The upstream regions flanking the 5Ј ends of the stx genes were reported to be conserved and continuous with phage sequences in a number of Shiga toxin-encoding bacteriophages (32,39,44). Genes for rare tRNAs are located in the neighborhood of the stx 2 genes, and it was suggested that these could play a role in effective expression of Stx2 (23,38). Correspondingly, the region located upstream from the stxA 2e gene was found to be conserved in 95 (86.4%) of the Stx2e strains investigated here, pointing to a common origin of the stx 2e genes in most of the strains.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Major Types of Shiga Toxin 2e-Producing Escherichia coli Bacteria Present in Food, Pigs, and the Environment as Potential Pathogens for Humans

Beutin¹,

Krüger²,

Krause³

et al. 2008

Appl Environ Microbiol

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Shiga toxin 2e (Stx2e)-producing strains from food (n ‫؍‬ 36), slaughtered pigs (n ‫؍‬ 25), the environment (n ‫؍‬ 21), diseased pigs (n ‫؍‬ 19), and humans (n ‫؍‬ 9) were investigated for production of Stx2e by enzymelinked immunosorbent assay, for virulence markers by PCR, and for their serotypes to evaluate their role as potential human pathogens. Stx2e production was low in 64% of all 110 strains. Stx2e production was inducible by mitomycin C but differed considerably between strains. Analysis by nucleotide sequencing and transcription of stx 2e genes in high-and low-Stx2e-producing strains showed that toxin production correlated with transcription rates of stx 2e genes. DNA sequences specific for the int, Q, dam, and S genes of the stx 2e bacteriophage P27 were found in 109 strains, indicating cryptic P27-like prophages, although 102 of these were not complete for all genes tested. Genes encoding intimin (eae), enterohemorrhagic Escherichia coli hemolysin (ehx), or other stx 1 or stx 2 variants were not found, whereas genes for heat-stable enterotoxins STI, STII, or EAST1 were present in 54.5% of the strains. Seven major serotypes that were associated with diseased pigs (O138:H14, O139:H1, and O141:H4) or with slaughter pigs, food, and the environment (O8:H4, O8:H9, O100:H30, and O101:H9) accounted for 60% of all Stx2e strains. The human Stx2e isolates did not belong to these major serotypes of Stx2e strains, and high production of Stx2e in human strains was not related to diarrheal disease. The results from this study and other studies do not point to Stx2e as a pathogenicity factor for diarrhea and hemolytic uremic syndrome in humans.

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“…AGA codons occur at high frequency in toxin-encoding genes of E. coli O157:H7 (31), and the cognate tRNA Arg (anticodon UCU) occurs in eight copies in this bacterium (as annotated in the genome NC_002695). Therefore, AGA_AGA is not shift prone in O157:H7 and is not avoided.…”

Section: Discussionmentioning

confidence: 99%

Expression Levels Influence Ribosomal Frameshifting at the Tandem Rare Arginine Codons AGG_AGG and AGA_AGA in Escherichia coli

et al. 2005

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The rare codons AGG and AGA comprise 2% and 4%, respectively, of the arginine codons of Escherichia coli K-12, and their cognate tRNAs are sparse. At tandem occurrences of either rare codon, the paucity of cognate aminoacyl tRNAs for the second codon of the pair facilitates peptidyl-tRNA shifting to the ؉1 frame. However, AGG_AGG and AGA_AGA are not underrepresented and occur 4 and 42 times, respectively, in E. coli genes. Searches for corresponding occurrences in other bacteria provide no strong support for the functional utilization of frameshifting at these sequences. All sequences tested in their native context showed 1.5 to 11% frameshifting when expressed from multicopy plasmids. A cassette with one of these sequences singly integrated into the chromosome in stringent cells gave 0.9% frameshifting in contrast to two-to four-times-higher values obtained from multicopy plasmids in stringent cells and eight-times-higher values in relaxed cells. Thus, ؉1 frameshifting efficiency at AGG_AGG and AGA_AGA is influenced by the mRNA expression level. These tandem rare codons do not occur in highly expressed mRNAs.

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Genes for tRNAArg Located in the Upstream Region of the Shiga Toxin II Operon in Enterohemorrhagic Escherichia coli O157:H7

Abstract: We found two genes for tRNA(Arg) in the region upstream of genes for Shiga-like toxin type II (SLT-II) in Escherichia coli O157:H7. The two encoded forms of tRNA(Arg) recognize rare codons in E. coli K12 but these rare codons occur in the toxin genes at high frequency.

Cited by 10 publications

References 19 publications

The Chromosome of Shigella flexneri Bacteriophage Sf6: Complete Nucleotide Sequence, Genetic Mosaicism, and DNA Packaging

The Chromosome of Shigella flexneri Bacteriophage Sf6: Complete Nucleotide Sequence, Genetic Mosaicism, and DNA Packaging

Evaluation of Major Types of Shiga Toxin 2e-Producing Escherichia coli Bacteria Present in Food, Pigs, and the Environment as Potential Pathogens for Humans

Expression Levels Influence Ribosomal Frameshifting at the Tandem Rare Arginine Codons AGG_AGG and AGA_AGA in Escherichia coli

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