Glider and vision: two new families of miniature inverted-repeat transposable elements in Xenopus laevis genome

We have characterised from Xenopus laevis two new short interspersed repeti tive elements, we have named Glider and Vision, that belong to the family o f miniature inverted-repeat transposable elements (MITEs). Glider was first characterised in an intronic region of the alpha -tropomyosin (alpha -TM) gene and database search has revealed the presence of this element in 10 ot her Xenopus laevis genes. Glider elements are about 150 bp long and for som e of them, their terminal inverted repeats are flanked by potential target- site duplications. Evidence for the mobility of Glider element has been pro vided by the presence/absence of one element at corresponding location in d uplicated alpha -TM genes. Vision element has been identified in the promot er region of the cyclin dependant kinase 2 gene (cdk2) where it is boxed in a Glider element. Vision is 284 bp long and is framed by 14-bp terminal in verted repeats that are flanked by 7-bp direct repeats. We have estimated t hat there are about 20,000 and 300 copies of Glider and Vision respectively scattered throughout the laevis genome. Every MITEs elements but two descr ibed in our study are found either in 5' or in 3' regulatory regions of gen es suggesting a potential role in gene regulation.