THE PRIMER TRANSFER-RNA SEQUENCE IS NOT INHERITED DURING TY1 RETROTRANSPOSITION

Yeast retrotransposon Ty1 transposes through an RNA intermediate by a mechanism resembling retroviral replication. Long terminal repeat retr oelements require primers for initiation of reverse transcription. The primer for minus strand DNA synthesis is the 3' end of a cellular tRN A that base pairs to the complementary region of genomic RNA (the prim er binding site). The genomic RNA of retroviruses and retrotransposons is shorter than its proviral DNA counterpart, lacking complete long t erminal repeats. A variety of models have been proposed to describe ho w complete long terminal repeats are regenerated during reverse transc ription. A common feature of these models is the requirement that the 3' portion of the primer tRNA be reverse-transcribed and then utilized in a strand-transfer reaction. We introduced a silent mutation into t he Ty1 primer binding site and followed its fate during a single cycle of reverse transcription to directly test this aspect of the reverse transcription model. We demonstrate that the tRNA sequence is not inhe rited by progeny Ty1 elements during reverse transcription.