Characterization of the relationship between integrase, excisionase and antirepressor activities associated with a superinfecting Shiga toxin encoding bacteriophage

Shigatoxigenic Escherichia coli emerged as new food borne pathogens in the early 1980s, primarily driven by the dispersal of Shiga toxin-encoding lambdoid bacteriophages. At least some of these Stx phages display superinfection phenotypes, which differ significantly from lambda phage itself, driving...

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Bibliographic Details
Published in:Nucleic acids research 2011-03, Vol.39 (6), p.2116-2129
Main Authors: Fogg, P C M, Rigden, D J, Saunders, J R, McCarthy, A J, Allison, H E
Format: Article
Language:English
Subjects:
Coliphages - enzymology
Coliphages - genetics
Computational Biology
DNA Nucleotidyltransferases - chemistry
DNA Nucleotidyltransferases - metabolism
Escherichia coli
Genome Integrity, Repair and
Integrases - genetics
Integrases - metabolism
Models, Molecular
Shiga-Toxigenic Escherichia coli - virology
Transcription Initiation Site
Viral Proteins - chemistry
Viral Proteins - metabolism
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Summary:Shigatoxigenic Escherichia coli emerged as new food borne pathogens in the early 1980s, primarily driven by the dispersal of Shiga toxin-encoding lambdoid bacteriophages. At least some of these Stx phages display superinfection phenotypes, which differ significantly from lambda phage itself, driving through in situ recombination further phage evolution, increasing host range and potentially increasing the host's pathogenic profile. Here, increasing levels of Stx phage Φ24(B) integrase expression in multiple lysogen cultures are demonstrated along with apparently negligible repression of integrase expression by the cognate CI repressor. The Φ24(B) int transcription start site and promoter region were identified and found to differ from in silico predictions. The unidirectional activity of this integrase was determined in an in situ, inducible tri-partite reaction. This indicated that Φ24(B) must encode a novel directionality factor that is controlling excision events during prophage induction. This excisionase was subsequently identified and characterized through complementation experiments. In addition, the previous proposal that a putative antirepressor was responsible for the lack of immunity to superinfection through inactivation of CI has been revisited and a new hypothesis involving the role of this protein in promoting efficient induction of the Φ24(B) prophage is proposed.
ISSN:0305-1048
1362-4962
DOI:10.1093/nar/gkq923