Genomic portrayal of IS4 family : modular insertion sequences, mobile insertion cassettes and overall family snapshot
(2008)
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- Authors
- Supervisors
- Mahillon, Jacques
- Abstract
- Prokaryotic mobile genetic elements (MGEs) are segments of DNA able to transfer themselves between cells, such as bacteriophages or plasmids, or to move within genomes, as do insertion sequences (ISs) and other transposons. MGEs are currently regarded as combinations of interchangeable modules. These modules usually provide the enzymes assuring mobility of MGEs, but some of them offer selective advantages, either for MGEs, or for their bacterial hosts. Both mobility and accessory functions of MGEs can have a considerable impact on the lifestyle and evolution of their prokaryotic hosts. In particular, ISs have the potential to multiply in genomes and to trigger extensive genome reshufflings. In the present work, the impact of MGEs was assessed through the study of one specific family, namely IS4. A novel genome rearranger, named MIC231A1 (Mobile Insertion Cassette), was recently reported in this family. MIC231A1 encodes an active D-stereospecific endopeptidase (ADP) flanked by the terminal inverted repeats of an IS4 element called IS231A. The IS231A transposase is able to transfer the MIC231A1 cassette in trans, allowing intragenomic transfers of the adp gene. To evaluate the biological relevance of MIC231A1, the diversity and distribution of IS231-MIC231 elements was evaluated in Bacillus cereus sensu lato, their natural host. They displayed an extensive modularity associated with trans-transposition of a diverse set of functions, including antibiotic resistance, transcriptional regulation and peptidase activities. In addition, the global impact, including distribution and copy number, of the entire IS4 family was explored in 540 completely sequenced prokaryotic genomes. This revealed that IS4 elements expand only on rare occasions, and only in certain strains, leading to interesting predictions of IS dynamics on evolutionary timescales. Hence, ISs turned out to be manageable parasites, and their potential to contribute to genome flexibility was extended to intracellular cis and trans transfer capabilities of accessory functions.
- Affiliations
Citations
De Palmenaer, D. (2008). Genomic portrayal of IS4 family : modular insertion sequences, mobile insertion cassettes and overall family snapshot. https://hdl.handle.net/2078.5/98485