Differential repair of excision gaps generated by transposable elements of the ‘Ac family’

Abstract

Studies on transposable elements of the Ac family have led to different models for excision gap repair in either plants or Drosophila. Excision products generated by the plant transposable elements Ac and Tam3 imply a more or less straightforward ligation of broken ends; excision products of the Drosophila P element indicate the involvement of 'double-strand break' (DSB) repair. Recent findings that excision products of Ac and Tam3 can also contain traces of the element ends indicate, however, that DSB repair might be an alternative repair mechanism in plants. A functional DSB repair mechanism in plants can also be deduced from the observed rapid increases of Ac copy number during plant development and from the involvement of Ac in the generation of internal Ac deletions. On the other hand, alternative repair mechanisms may also be functional in Drosophila, because some of the 'footprints' generated upon P excision can be explained by a mechanism that has been postulated for excision gap repair in plants. It is concluded that plants and Drosophila can use similar repair mechanisms, but that the predominance of a certain repair mechanism is determined by the host.

Identification of novel intergenic repetitive units in a mycobacterial two‐component system operon

“…7B). Similar to what is observed for transposable elements in other organisms (Rommens et al, 1993), this sequence may be the residual duplicated target sequence left over after the excision of the MIRU from its insertion site in M. leprae. In both cases, these duplications correspond to the overlapping stop and start codons of two contiguous genes (encoding two unknown products, and Rf1 and HemK respectively), which is compatible with a transposition mechanism involving duplication of flanking basepairs at the target site.…”

TheHermes element fromMusca domestica can transpose in four families of cyclorrhaphan flies

“…Members of the hobo, Ac, and Tam3 (hAT) transposable element family share limited sequence similarity (Calvi et al, I991;Feldmar & Kunze, 1991;, a common mechanism of excision leading to excision reaction products with similar structures (Atkinson, Warren & O'Brochta, 1993; Rommens et al, 1993), and an ability to function when introduced into non-host species (Hehl, 1994;O'Brochta et al, 1994;Pinkerton, O'Brochta & Atkinson, 1996). As reported in this study, the Hermes element from the house fly M. domestica also is able to function in non-host species.…”

Gene replacement

“…However, if a more subtle mutation of the gene of interest is required then excision of the transposable element could be induced in the presence of a targeting vector resulting in a targeted mutation. However, a theoretical comparison of the models of excision of plant transposable elements and Drosophila elements suggests that the DSB mechanism may only play a minor role in the excision of transposable elements in plants [59] thus restricting the possible usefulness of this protocol.…”