DISRUPTION OF 3 PHOSPHATIDYLINOSITOL-POLYPHOSPHATE 5-PHOSPHOTOSE GENES FROM SACCHAROMYCES-CEREVISIAE RESULTS IN PLEIOTROPIC ABNORMALITIES OF VACUOLE MORPHOLOGY, CELL-SHAPE, AND OSMOHOMEOSTASIS

As a result of the genome sequencing project in Saccharomyces cerevisi ae, three open reading frames were found in the yeast genome that cont ain sequences with strong homology to all the domains conserved among the four mammalian phosphatidylinositol-phosphate 5-phosphatases: inpp 5bp, ocrl1p, synaptojanin, and ship. In addition, all three yeast gene products shared with synaptojanin regions of homology to the SAC1 gen e of yeast. Disruption of each of these genes singly and in pairs prod uced mutant strains that were viable but demonstrated variable phenoty pes of abnormal vacuolar and plasma membrane morphology as well as inc reased sensitivity to osmotic stress. Total phosphatidylinositol-(4,5) -bisphosphate 5-phosphatase activity was reduced to varying degrees in each of the strains. No defect in carboxypeptidase Y sorting was seen in a processing and targeting assay. Abnormal actin cytoskeleton morp hology was present in some of the strains carrying mutations in two of the genes.