IN-FRAME LINKER INSERTION MUTAGENESIS OF YEAST TRANSPOSON TY1 - PHENOTYPIC ANALYSIS

A plasmid bearing a transpositionally functional GAL1::Ty1 fusion was mutagenized by insertion of four or five codons semirandomly throughou t the plasmid. This collection of mutant plasmids was introduced into yeast cells and studied with regard to the properties of the mutant Ty 1-encoded proteins and the transposition phenotypes observed. All of t he transposition-inactivating mutations were previously found to be re cessive with the exception of a single mutation in TYA. In this mutant , TYA protein of normal abundance is produced, but the virus-like part icles containing this protein are unstable and have aberrant behavior. The effects of mutations in noncoding regions, as well as the capsid protein coding region TYA, and the regions encoding the protease, inte grase and reverse transcriptase proteins are described. Effects on gen e expression, types of proteins produced, proteolysis of precursor pro teins, virus-like particle structure, and biochemical activities of th e encoded proteins are summarized. In addition, we show that one of th e mutations in the 3' LTR represents a new nonessential site into whic h foreign marker DNA can be inserted without compromising transpositio n.