The yeast retrotransposons Ty1 and Ty3 require the RNA lariat debranching enzyme, Dbr1p for efficient accumulation of reverse transcripts

A mutant screen has been initiated to identify host genes important for the replication of retrotransposons in Saccharomyces cerevisiae. Two mutants w ere identified that undergo Ty1 and Ty3 transposition at <10% of the wild-t ype frequency, Both these mutants have deficiencies in the accumulation of full-length Ty1 and Ty3 cDNAs, although Ty proteins (including reverse tran scriptase) accumulate at wildtype levels. The DBR1 gene, encoding the yeast debranching enzyme, complements both mutants. This suggests that Dbr1p is important for either reverse transcription or the stability of Ty cDNA, rol es that have not been previously reported for this protein. The deficiency in accumulation of Ty cDNAs in dbr1 mutants is apparent when engineered Ty elements are expressed for short time periods (6-10 h) but is not apparent following long expression periods (>24 h). (C) 2000 Academic Press.