title: PIK1, an essential phosphatidylinositol 4-kinase associated with the yeast nucleus.
abstract: 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 Ca2+. 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.
authors.affiliation: Department of Biochemistry, University of Basel, Switzerland.
authors.forename: J F
authors.initials: JF
authors.lastname: Garcia-Bustos
authors.forename: F
authors.initials: F
authors.lastname: Marini
authors.forename: I
authors.initials: I
authors.lastname: Stevenson
authors.forename: C
authors.initials: C
authors.lastname: Frei
authors.forename: M N
authors.initials: MN
authors.lastname: Hall
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase; D000595:Amino Acid Sequence; D001483:Base Sequence; D002451:Cell Compartmentation; D002455:Cell Division / Q000235:genetics; D002467:Cell Nucleus / Q000737:chemistry*; D003001:Cloning, Molecular; D005800:Genes, Fungal / Q000235:genetics*; D005816:Genetic Complementation Test; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D008969:Molecular Sequence Data; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D015544:Inositol 1,4,5-Trisphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); D019870:1-Phosphatidylinositol 4-Kinase; C441760:PIK1 protein, S cerevisiae