The yeast retrotransposon Ty1 transposes through an RNA intermediate by a mechanism similar to that of retroviral reverse transcription and integration. Ty1 RNA contains a putative minus strand primer binding site (-PBS) that is complementary to the 3′ acceptor stem of the initiator methionine tRNA (tRNAiMet). Here we demonstrate that the tRNAiMet is used as a primer for Ty1 reverse transcription. Mutations in the Ty1 element that alter 5 of 10 nucleotides that are complementary to the tRNAiMet abolish Ty1 transposition, even though they are silent with regard to Ty1 protein coding. We have constructed a yeast strain lacking wild-type tRNAiMet that is dependent on a mutant derivative of tRNAiMet that has an altered acceptor stem sequence, engineered to restore homology with the Ty1 -PBS mutant. The compensatory mutations made in the tRNAiMet alleviate the transposition defect of the Ty1 -PBS mutant. The mutant and wild-type tRNAiMet are enriched within Ty1 virus-like particles irrespective of complementarity to the Ty1 -PBS. Thus, complementarity between the Ty1 -PBS and tRNAiMet is essential for transposition but is not necessary for packaging of the tRNA inside virus-like particles.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - 1992|
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