University of SaskatchewanHARVEST
  • Login
  • Submit Your Research
  • About
    • About HARVEST
    • Guidelines
    • Browse
      • All of HARVEST
      • Communities & Collections
      • By Issue Date
      • Authors
      • Titles
      • Subjects
      • This Collection
      • By Issue Date
      • Authors
      • Titles
      • Subjects
    • My Account
      • Login
      JavaScript is disabled for your browser. Some features of this site may not work without it.
      View Item 
      • HARVEST
      • Electronic Theses and Dissertations
      • Graduate Theses and Dissertations
      • View Item
      • HARVEST
      • Electronic Theses and Dissertations
      • Graduate Theses and Dissertations
      • View Item

      Schizosaccharomyces pombe Phosphatidylinositol 4-kinase, Pik1p, in cell cycle control

      Thumbnail
      View/Open
      Park_May2007.pdf (8.950Mb)
      Date
      2007-05-15
      Author
      Park, Jae-Sook
      Type
      Thesis
      Degree Level
      Doctoral
      Metadata
      Show full item record
      Abstract
      Pik1p, one of three phosphatidylinositol 4-kinases in the fission yeast, Schizosaccharomyces pombe, was found previously to interact with Cdc4p, a myosin essential light chain that is required for cytokinesis. The involvement of pik1 in cell cycle control was investigated. A fluorescently tagged Pik1p fusion protein was associated with Golgi throughout the cycle, and was found at the medial division plane of the cell during late cytokinesis. This latter distribution has not been reported previously. Gene deletion in diploid cells and tetrad analysis revealed that pik1 is essential for cell viability and is required for spore germination. The terminal phenotype of a temperature-sensitive, loss-of-function allele (pik1-td) indicated that pik1 is involved in cytokinesis: particularly for suppression of secondary septum material deposition, for suppression of initiation of supernumerary septa, and for cell separation. Contractile ring formation was normal in pik1-td cells at the restrictive temperature although the pattern of F-actin patches was disrupted. The F-actin patches were dispersed throughout the cytoplasm. Accumulation of extra inner membranous or vesicle-like structures was observed in these cells. The S. pombe nmt1 promoter and attenuated versions of it were found to be useful for complementation studies in S. cerevisiae. Heterologous expression of S. pombe pik1 complemented the essential functions of a temperature-sensitive allele (pik1-101) of its orthologue in Saccharomyces cerevisiae that were lost at the restrictive temperature. A residue required for S. pombe Pik1p lipid kinase activity, D709, was also required for this complementation. A residue, R838, which is required for interactions between Pik1p and Cdc4p was not required for this complementation. The timing and localization of Pik1p to the division plane of the cell late in cytokinesis combined with analysis of the terminal phenotype of a loss-of-function allele, indicate that Pik1p and/or its derived phosphoinositides are required for regulation of septation and cell separation. Pik1p may be involved in the transport, possibly via vesicular transport, of enzymes required for hydrolysis of the primary septum. It may be involved in signaling pathways that lead to the initiation of septation and to the cessation of the deposition of secondary septum material.
      Degree
      Doctor of Philosophy (Ph.D.)
      Department
      Microbiology and Immunology
      Program
      Microbiology and Immunology
      Supervisor
      Hemmingsen, Sean M.; Desautels, Michel
      Committee
      Xiao, Wei; Kaminskyj, Susan G. W.; Harkness, Troy
      Copyright Date
      May 2007
      URI
      http://hdl.handle.net/10388/etd-05142007-092045
      Subject
      lipid kinases
      cell separation
      septation
      cytokinesis
      lipid phosphatases
      Collections
      • Graduate Theses and Dissertations
      University of Saskatchewan

      University Library

      © University of Saskatchewan
      Contact Us | Disclaimer | Privacy