Gene ste20 controls amiloride sensitivity and fertility in Schizosaccharomyces pombe

It has been shown previously that amiloride, a widely used diuretic drug, i nhibits growth in Schizosaccharomyces pombe. Here we show that the drug als o alleviates repression by various nutrients of mating and sporulation in f ission yeast. We selected spontaneous mutants that are amiloride-resistant and unable to mate and sporulate. One of them defines the gene ste20. This gene has been cloned and sequenced. It codes for a putative protein of 1309 amino acids. Its sequence does not provide any clues to its function. In c ontrast to the wild-type, mutants defective in this gene can grow in a medi um containing 40 mu m amiloride, do not arrest in G(1), and do not induce s te11 expression upon nitrogen starvation and thus are sterile. In addition the ste20 mutants are methylamine-sensitive, exhibit enhanced medium acidif ication and are defective in the utilization of gycerol as a carbon source.