A novel pseudoautosomal human gene encodes a putative protein similar to Ac-like transposases

We report the cloning of a novel gene, called Tramp, in the Xp/Yp PAR regio n that has a functional homologue on the Y chromosome and escapes X-inactiv ation. This gene encodes, within a single exon, a putative protein that has amino acid similarity with transposases of the Ac family. Flanking this ge ne we have identified putative terminal inverted repeats (TIRs) and a dupli cate target site, suggesting that it may be an ancient transposable element . The nucleotide differences in these sites and the TIR-binding inactivity of the putative Tramp protein suggest that this element is not an autonomou s transposon. In the human genome, the Tramp protein may be involved in the transposition of other transposable elements, like medium reiterated frequ ency repeats, or it could be specialized in the acquisition of a new cellul ar function.