ISOLATION AND CHARACTERIZATION OF A NOVEL YEAST GENE, ATH1, THAT IS REQUIRED FOR VACUOLAR ACID TREHALASE ACTIVITY

We have isolated a plasmid containing a gene, ATH1, that results in eight- to ten-fold higher acid trehalase activity in yeast cells when present in high copy. The screening procedure was based on overproduction-induced mislocalization of acid trehalase activity; overproduction of vacuolar enzymes that transit through the secretory pathway leads to secretion to the cell surface. A DNA fragment that confers cell surface expression of acid trehalase activity was cloned and sequenced. The deduced amino acid sequence displayed no homology to known proteins, indicating that we have identified a novel gene. A deletion in the genomic copy of the A TH1 gene eliminates vacuolar acid trehalase activity. These results suggest that ATH1 may be the structural gene encoding vacuolar acid trehalase or that the gene product may be an essential regulatory component involved in control of trehalase activity. The sequence has been deposited in the GenBank data library under Accession Number X84156 S, cerevisiae ATH1 gene.