Ty-mediated gene expression of the LYS2 and HIS4 genes of Saccharomyces cerevisiae is controlled by the same SPT genes.

Five Ty insertion mutations were isolated at the LYS2 locus of Saccharomyces cerevisiae. Genetic and physical analyses show that four Ty insertions are in the 5' noncoding region of LYS2 and one is within the structural gene. Three of these Ty elements have been cloned and characterized. The Ty mutations differ from each other in restriction pattern, phenotypic effects on LYS2, reversion frequency, and the nature of reversion events. Spt2 and spt3 mutations, known to suppress Ty insertions and their solo delta derivatives at HIS4, can also suppress at least one of the Ty insertions (Ty61) at LYS2 and can also suppress the Lys- phenotype of a solo delta derivative of another Ty insertion (Ty128) at LYS2. These results demonstrate that spt mutations can suppress Ty and delta mutations at both HIS4 and LYS2, suggesting that they are general for their effects on Ty and delta elements.