Ty3/gypsy-like retrotransposons in Candida albicans and Candida dubliniensis: Tca3 and Tcd3

Ty3/gypsy retrotransposons are a widespread group of eukaryote mobile genetic elements. They are similar in structure to, and may be ancestors of, the vertebrate retroviruses. Here we describe the first Ty3/gypsy retrotransposons from the pathogenic yeasts Candida albicans and Candida dubliniensis, which we refer to as Tca3 and Tcd3, respectively. Tca3 was first identified in a variety of strains as an element lacking a large part of its coding region. Comparative analyses between C. albicans and C. dubliniensis allowed us to identify the closely related full-length Tcd3 element, and, subsequently, the full-length Tca3 elements. The full-length versions of Tca3 and Tcd3 are broadly similar in structure to other Ty3/gypsy elements, but have several features of special interest, e.g. both elements appear to have a novel mechanism for priming minus-strand DNA synthesis, probably involving conserved secondary structures adjacent to the 5' LTRs. Also, while closely related to each other, the two elements appear to be fairly distantly related to other known Ty3/gypsy-like elements. Finally, the occurrence of the internally deleted forms of Tca3 in many strains raises interesting questions concerning the evolution of these transposable elements in Candida and the evolution of Candida itself. The sequences reported in this paper have been assigned GenBank Accession Nos AF499463, AF499464 and AF510498.