STP1, A GENE INVOLVED IN PRE-TRNA PROCESSING IN YEAST, IS IMPORTANT FOR AMINO-ACID UPTAKE AND TRANSCRIPTION OF THE PERMEASE GENE BAP2

The bap1 mutant of Saccharomyces cerevisiae was previously isolated by its reduced uptake of branched-chain amino acids. In the present study, the corresponding wild-type gene was cloned and partial sequencing and subsequent genetic analysis revealed identity to STP1, a gene involved in tRNA maturation. The decrease in amino-acid uptake caused by stp1 mutations is independent of GCN4. It was previously found that the BAP2 promoter can be activated by the presence of amino acids, notably leucine, in the medium. We found that this activation depends on STP1. As a simple hypothesis we propose that Stp1p is a transcription factor which activates BAP2, and probably other amino-acid permease genes.