title: The Spg1p GTPase is an essential, dosage-dependent inducer of septum formation in Schizosaccharomyces pombe.
abstract: The spg1 gene (septum-promoting GTPase) was cloned as a multicopy suppressor of a dominant-negative mutant of the Cdc7p kinase. It encodes a small GTPase of the Ras superfamily. spg1 is an essential gene. Null or heat-sensitive alleles do not make a division septum, but growth, S-phase, and mitosis continue in the absence of cell division, producing elongated, multinucleate cells. Increased expression of Spg1p induces septum formation in G2, S-phase, and pre-Start G1-arrested cells. This requires the activity of Cdc7p kinase, but not p34(cdc2). Increased expression of Cdc7p bypasses the requirement for Spg1p. Spg1p and Cdc7p can be coimmunoprecipitated from cell extracts, and interact in the two-hybrid system. These data indicate that Spg1p is a key element in controlling the onset of septum formation in Schizosaccharomyces pombe, and that it acts through the Cdc7p kinase.
authors.affiliation: Cell Cycle Control Laboratory, Swiss Institute for Experimental Cancer Research (ISREC), Epalinges.
authors.forename: S
authors.initials: S
authors.lastname: Schmidt
authors.forename: M
authors.initials: M
authors.lastname: Sohrmann
authors.forename: K
authors.initials: K
authors.lastname: Hofmann
authors.forename: A
authors.initials: A
authors.lastname: Woollard
authors.forename: V
authors.initials: V
authors.lastname: Simanis
mesh_terms: D000595:Amino Acid Sequence; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002455:Cell Division; D020558:GTP Phosphohydrolases / Q000097:blood / Q000737:chemistry / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D005838:Genotype; D008938:Mitosis; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010750:Phosphoproteins / Q000378:metabolism; D010802:Phylogeny; D017354:Point Mutation; D011494:Protein Kinases / Q000096:biosynthesis; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D015183:Restriction Mapping; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins / Q000097:blood / Q000737:chemistry / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: D018797:Cell Cycle Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; D029702:Schizosaccharomyces pombe Proteins; D011494:Protein Kinases; C489406:cdc7 protein, S pombe; D017346:Protein Serine-Threonine Kinases; D020558:GTP Phosphohydrolases; C510604:Spg1 protein, S pombe