In-frame linker insertion mutagenesis of yeast transposon Ty1: mutations, transposition and dominance

A plasmid bearing a GAL1::Tyl fusion that is competent to transpose was mutagenized by insertion of oligodeoxyribo-nucleotides that precisely introduce four or five codons semirandomly throughout the plasmid. Approximately one quarter of these resulted in inactivation of transposition; these include inactivating insertions in both the TYA and TYB genes, corresponding to retroviral gag and pol genes. Examples of transposition-inactivating mutations map within each of the known or proposed functional domains of TYB, suggesting that these are all required for retrotransposition. All of the transposition-inactivating mutations were found to be recessive with the exception of a single mutation in TYA. The remaining mutations have slightly deleterious to no effect on Ty1 transposition.