CHARACTERIZATION OF SCHIZOSACCHAROMYCES-POMBE HIS1 AND HIS5 CDNAS

We have isolated Schizosaccharomyces pombe cDNAs corresponding to the genes his1(+) and his5(+). The his1 cDNA was isolated by functional co mplementation of the His(-) phenotype in a his1-29 gen3 Saccharomyces cerevisiae strain, while the his5 cDNA was isolated as a suppressor of the 3-amino-1,2,4-triazole (3-AT) sensitivity in a gen3 S. cerevisiae strain. his1 and his5 are each present in single copy in haploid S. p ombe. As is the case with S. cerevisiae, we have found that the growth of wild-type strains of S. pombe is sensitive to 3-AT, an inhibitor o f imidazoleglycerol-phosphate dehydratase. This enzyme is encoded by t he HIS3 gene in S. cerevisiae and the his5(+) gene in S. pombe. Treatm ent of S. pombe cells with 3-AT leads to a small increase in the level of the his5 transcript, but no effect is seen on the level of the his 1 transcript. This is in contrast to larger increases in transcription of amino acid biosynthetic genes, regulated by the general amino acid control, seen previously in similarly treated cultures of S. cerevisi ae. These results suggest that there are likely to be some differences in the regulation of amino acid biosynthesis between these two yeasts . Sequences reported here have been deposited with GenBank as U07830 ( his1) and U07831 (his5).