Dynamics of the SetCD-Regulated Integration and Excision of Genomic Islands Mobilized by Integrating Conjugative Elements of the SXT/R391 Family

Mobilizable genomic islands (MGIs) are small genomic islands that are mobilizable by SXT/R391 integrating conjugative elements (ICEs) due to similar origins of transfer. Their site-specific integration and excision are catalyzed by the integrase that they encode, but their conjugative transfer entir...

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Bibliographic Details
Published in:Journal of Bacteriology 2012-11, Vol.194 (21), p.5794-5802
Main Authors: Daccord, Aurélie, Mursell, Mathias, Poulin-Laprade, Dominic, Burrus, Vincent
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Bacteriology
Biological and medical sciences
Chromosomes
Fundamental and applied biological sciences. Psychology
Gene expression
genes
Genomic Islands
Genomics
Gram-Negative Bacteria - genetics
Interspersed Repetitive Sequences
Microbiology
Miscellaneous
Molecular Sequence Data
Plasmids
Proteins
Recombinases - biosynthesis
Recombination, Genetic
Sequence Alignment
transcription factors
Transcription Factors - metabolism
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Summary:Mobilizable genomic islands (MGIs) are small genomic islands that are mobilizable by SXT/R391 integrating conjugative elements (ICEs) due to similar origins of transfer. Their site-specific integration and excision are catalyzed by the integrase that they encode, but their conjugative transfer entirely depends upon the conjugative machinery of SXT/R391 ICEs. In this study, we report the mechanisms that control the excision and integration processes of MGIs. We found that while the MGI-encoded integrase IntMGI is sufficient to promote MGI integration, efficient excision from the host chromosome requires the combined action of IntMGI and of a novel recombination directionality factor, RdfM. We determined that the genes encoding these proteins are activated by SetCD, the main transcriptional activators of SXT/R391 ICEs. Although they share the same regulators, we found that unlike rdfM, intMGI has a basal level of expression in the absence of SetCD. These findings explain how an MGI can integrate into the chromosome of a new host in the absence of a coresident ICE and shed new light on the cross talk that can occur between mobilizable and mobilizing elements that mobilize them, helping us to understand part of the rules that dictate horizontal transfer mechanisms.
ISSN:0021-9193
1098-5530
1067-8832
DOI:10.1128/JB.01093-12