title: Novel fission yeast Cdc7-Dbf4-like kinase complex required for the initiation and progression of meiotic second division.
abstract: Cdc7, a conserved serine/threonine protein kinase, controls initiation of DNA replication. A regulatory subunit, Dbf4, stimulates the kinase activity of Cdc7 and recruits it to the replication origins. Schizosaccharomyces pombe has a homologous kinase complex, composed of Hsk1 and Dfp1/Him1. Here, we report a novel protein kinase of S. pombe, Spo4, which shares common structural features with the Cdc7 kinases. In spite of the structural similarities, Spo4 is dispensable for mitotic growth and premeiotic DNA replication. Intriguingly, spo4 null mutants are defective in initiation and progression of the second meiotic division. Spindles for meiosis II are often fragmented. Spo4 kinase activity is markedly enhanced when the enzyme is associated with its regulatory subunit, Spo6, a Dbf4-like protein. Expression of Spo4 is specifically induced during meiosis. Spo4 is preferentially present in nuclei, but this nuclear localization does not require Spo6. These results suggest that Spo4 is a Cdc7 kinase whose primary role is in meiosis, not in DNA replication. This is the first report of an organism which has two Cdc7-related kinase complexes with different biological functions.
authors.affiliation: Department of Biology, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Nakamura
authors.forename: Michiko
authors.initials: M
authors.lastname: Nakamura-Kubo
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Nakamura
authors.forename: Chikashi
authors.initials: C
authors.lastname: Shimoda
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005434:Flow Cytometry; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D006801:Humans; D046911:Macromolecular Substances; D008540:Meiosis / Q000502:physiology*; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C088096:Dbf4 protein, S cerevisiae; D005656:Fungal Proteins; D046911:Macromolecular Substances; D009687:Nuclear Proteins; C103266:PAT1 protein, S cerevisiae; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D004247:DNA; C489404:CDC7 protein, S cerevisiae; C068619:CDC7 protein, human; C443677:Spo4 protein, S pombe; C489406:cdc7 protein, S pombe; C094761:HSK1 protein, S pombe; D017346:Protein Serine-Threonine Kinases