Phosphatidylinositol-3 kinase in fission yeast: a possible role in stress responses.

A DNA fragment coding for a part of a putative phosphatidylinositol 3 kinase was cloned from Schizosaccharomyces pombe by cross-hybridization with Saccharomyces cerevisiae VPS34 gene, a yeast homologue of mammalian PI-3 kinase. The clone contained an open reading frame of 797 amino acids but lacked the initiation codon, ATG. The predicted amino acid sequence was homologous to those of S. cerevisiae VPS34 and mammalian PI-3 kinase genes. Disruption of the gene resulted in extremely low levels of PI-3-P and higher levels of PI-4-P, supporting the idea that the gene codes for the PI-3 kinase of S. pombe. The disruptants harbored large vacuoles and were sensitive to stresses such as high temperature or high concentration of monovalent and divalent cations.