PIK1, an essential phosphatidylinositol 4-kinase associated with the yeast nucleus
Garcia-Bustos, J.F.; Marini, F.; Stevenson, I.; Frei, C.; Hall, M.N.
EMBO Journal 13(10): 2352-2361
1994
ISSN/ISBN: 0261-4189 PMID: 8194527 Document Number: 438944
Transmission of mitogenic and developmental signals to intracellular targets is often mediated by inositol derivatives. Here we present the cloning and characterization of a gene from Saccharomyces cerevisiae, PIK1, encoding the enzyme that catalyses the first committed step in the production of the second messenger inositol-1,4,5-trisphosphate. PIK1 encodes a phosphatidylinositol 4-kinase (PI 4-kinase) essential for growth. Cells carrying PIK1 on a multicopy vector overexpress PI 4-kinase activity exclusively in a nuclear fraction, suggesting that PIK1 is part of a nuclear phosphoinositide cycle. Temperature-sensitive mutations, but not a null mutation, can be suppressed by high osmolarity or an elevated concentration of Ca-2+. Conditional mutants have a cytokinesis defect as indicated by a uniform terminal phenotype of cells with large buds and fully divided nuclei. We suggest that PIK1 controls cytokinesis through the actin cytoskeleton.