Dataset Information

Insertion sequence inversions mediated by ectopic recombination between terminal inverted repeats.

ABSTRACT: Transposable elements are widely distributed and diverse in both eukaryotes and prokaryotes, as exemplified by DNA transposons. As a result, they represent a considerable source of genomic variation, for example through ectopic (i.e. non-allelic homologous) recombination events between transposable element copies, resulting in genomic rearrangements. Ectopic recombination may also take place between homologous sequences located within transposable element sequences. DNA transposons are typically bounded by terminal inverted repeats (TIRs). Ectopic recombination between TIRs is expected to result in DNA transposon inversions. However, such inversions have barely been documented. In this study, we report natural inversions of the most common prokaryotic DNA transposons: insertion sequences (IS). We identified natural TIR-TIR recombination-mediated inversions in 9% of IS insertion loci investigated in Wolbachia bacteria, which suggests that recombination between IS TIRs may be a quite common, albeit largely overlooked, source of genomic diversity in bacteria. We suggest that inversions may impede IS survival and proliferation in the host genome by altering transpositional activity. They may also alter genomic instability by modulating the outcome of ectopic recombination events between IS copies in various orientations. This study represents the first report of TIR-TIR recombination within bacterial IS elements and it thereby uncovers a novel mechanism of structural variation for this class of prokaryotic transposable elements.

SUBMITTER: Ling A

PROVIDER: S-EPMC3004938 | biostudies-literature | 2010

REPOSITORIES: biostudies-literature

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Insertion sequence inversions mediated by ectopic recombination between terminal inverted repeats.

Ling Alison A Cordaux Richard R

PloS one 20101220 12

Transposable elements are widely distributed and diverse in both eukaryotes and prokaryotes, as exemplified by DNA transposons. As a result, they represent a considerable source of genomic variation, for example through ectopic (i.e. non-allelic homologous) recombination events between transposable element copies, resulting in genomic rearrangements. Ectopic recombination may also take place between homologous sequences located within transposable element sequences. DNA transposons are typically ...[more]

PMID: 21187977

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Project description:A new insertion sequence (IS) of Mycoplasma fermentans is described. This element, designated IS1630, is 1,377 bp long and has 27-bp inverted repeats at the termini. A single open reading frame (ORF), predicted to encode a basic protein of either 366 or 387 amino acids (depending on the start codon utilized), occupies most of this compact element. The predicted translation product of this ORF has homology to transposases of the IS30 family of IS elements and is most closely related (27% identical amino acid residues) to the product of the prototype of the group, IS30. Multiple copies of IS1630 are present in the genomes of at least two M. fermentans strains. Characterization and comparison of nine copies of the element revealed that IS1630 exhibits unusual target site specificity and, upon insertion, duplicates target sequences in a manner unlike that of any other IS element. IS1630 was shown to have the striking ability to target and duplicate inverted repeats of variable length and sequence during transposition. IS30-type elements typically generate 2- or 3-bp target site duplications, whereas those created by IS1630 vary between 19 and 26 bp. With the exception of two recently reported IS4-type elements which have the ability to generate variable large duplications (B. B. Plikaytis, J. T. Crawford, and T. M. Shinnick, J. Bacteriol. 180:1037-1043, 1998; E. M. Vilei, J. Nicolet, and J. Frey, J. Bacteriol. 181:1319-1323, 1999), such large direct repeats had not been observed for other IS elements. Interestingly, the IS1630-generated duplications are all symmetrical inverted repeat sequences that are apparently derived from rho-independent transcription terminators of neighboring genes. Although the consensus target site for IS30 is almost palindromic, individual target sites possess considerably less inverted symmetry. In contrast, IS1630 appears to exhibit an increased stringency for inverted repeat recognition, since the majority of target sites had no mismatches in the inverted repeat sequences. In the course of this study, an additional copy of the previously identified insertion sequence ISMi1 was cloned. Analysis of the sequence of this element revealed that the transposase encoded by this element is more than 200 amino acid residues longer and is more closely related to the products of other IS3 family members than had previously been recognized. A potential site for programmed translational frameshifting in ISMi1 was also identified.

Dataset Information

Insertion sequence inversions mediated by ectopic recombination between terminal inverted repeats.

Publications

Insertion sequence inversions mediated by ectopic recombination between terminal inverted repeats.

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