Movement of IS26-associated antibiotic resistance genes occurs via a translocatable unit that includes a single IS26 and preferentially inserts adjacent to another IS26.
Bottom Line: Intact transposase genes in both IS26s were required for high-frequency cointegrate formation as inactivation of either one reduced the frequency 30-fold.Conversion of each residue in the DDE motif of the Tnp26 transposase also reduced the cointegration frequency.IS26-flanked structures deceptively resemble class I transposons, but this work reveals that the features of IS26 movement do not resemble those of the IS and class I transposons studied to date.
Affiliation: School of Molecular Bioscience, The University of Sydney, Sydney, Australia.Show MeSH
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Mentions: The model presented here for the movement of IS26 together with a unique DNA segment explains how regions containing several copies of IS26 interspersed with different DNA segments containing antibiotic resistance genes or other genes arise. It also explains how the configuration of the tandem duplications that have been reported (Fig. 1B) are likely to have arisen. Moreover, the predictions of the model were able to be verified experimentally. Consequently, there are two distinct modes of movement for IS26. The first is cointegrate formation with duplication of the IS26 and generation of a target duplication, and the second is TU incorporation at an existing IS26 (Fig. 7). This feature is presumably shared by other members of the IS6 family, setting this IS family apart from other IS with DDE transposases.
Affiliation: School of Molecular Bioscience, The University of Sydney, Sydney, Australia.