Characterization of products of TY1-mediated reverse transcription in Saccharomyces cerevisiae.

Transposition of the yeast transposable element, Ty, has been shown to require a reverse transcription process. By analysing the extrachromosomal Ty-specific nucleic acid molecules associated with overproduced Ty virus-like particles (Ty-VLPs), we identified several reverse transcribed cDNA strands. Most of them resemble the characteristic intermediates of the reverse transcription process described for authentic retroviruses: a (-) strong-stop DNA strand covalently bound to an RNA primer, two elongated (-) strands with one or two long terminal repeat (LTR) sequences and a (+) strong-stop DNA. Surprisingly, complete (+) strands and full-length linear duplex Ty DNA could not be detected. The structural features of two additional (+) strands may indicate some differences between the mechanisms of (+) strand synthesis in Ty and other retrotransposons or retroviruses.