Mutations affecting Ty-mediated expression of the HIS4 gene of Saccharomyces cerevisiae.

We have identified mutations in seven unlinked genes (SPT genes) that affect the phenotypes of Ty and delta insertion mutations in the 5' noncoding region of the HIS4 gene of S. cerevisiae. Spt mutants were selected for suppression of his4-912 delta, a solo delta derivative of Ty912. Other Ty and delta insertions at HIS4 are suppressed by mutations in some but not all of the SPT genes. Only spt4 suppresses a non-Ty insertion at HIS4. In addition to their effects on Ty and delta insertions, mutations in several SPT genes show defects in general cellular functions--mating, DNA repair and growth.