CLONING OF THE SAT1 GENE CONCERNED WITH SALT TOLERANCE OF THE YEAST ZYGOSACCHAROMYCES-ROUXII

A gene complementing both NaCl hypersensitivity and a defect in the re gulation of the intracellular level of Na+ caused by a sat1 mutation i n Zygosaccharomyces rouxii was cloned from a genomic library of Z. rou xii NRRL 2547. Disruption of the cloned gene (SAT1) resulted in a defe ct in NaCl tolerance, intracellular accumulation of high levels of Na and low levels of K+ in the cells. The sat1(-) null mutant showed nor mal levels of tolerance against 15% KCl and 60% glucose. These phenoty pes were the same as those of the sat1 mutant. Furthermore, the sat1 m utation was not complemented by crossing with the sat1(-) null mutant. The cloned SAT1 gene was sequenced and was determined to have an open reading frame (ORF) coding for 327 amino acid residues. Northern blot analysis using the cloned gene as a probe indicated that the transcri pt synthesized in cells grown in the presence of 10% NaCl was about 1, 100 nucleotides in size, which was large enough to encode the SAT1 gen e product. SAT1 showed 53.5% similarity with the UGA43 of Saccharomyce s cerevisiae, a negative regulator of genes involved in the nitrogen a ssimilation pathway which contains a typical zinc-finger motif for DNA binding.