title: Cdk1 promotes cytokinesis in fission yeast through activation of the septation initiation network.
abstract: In Schizosaccharomyces pombe, late mitotic events are coordinated with cytokinesis by the septation initiation network (SIN), an essential spindle pole body (SPB)-associated kinase cascade, which controls the formation, maintenance, and constriction of the cytokinetic ring. It is not fully understood how SIN initiation is temporally regulated, but it depends on the activation of the GTPase Spg1, which is inhibited during interphase by the essential bipartite GTPase-activating protein Byr4-Cdc16. Cells are particularly sensitive to the modulation of Byr4, which undergoes cell cycle-dependent phosphorylation presumed to regulate its function. Polo-like kinase, which promotes SIN activation, is partially responsible for Byr4 phosphorylation. Here we show that Byr4 is also controlled by cyclin-dependent kinase (Cdk1)-mediated phosphorylation. A Cdk1 nonphosphorylatable Byr4 phosphomutant displays severe cell division defects, including the formation of elongated, multinucleate cells, failure to maintain the cytokinetic ring, and compromised SPB association of the SIN kinase Cdc7. Our analyses show that Cdk1-mediated phosphoregulation of Byr4 facilitates complete removal of Byr4 from metaphase SPBs in concert with Plo1, revealing an unexpected role for Cdk1 in promoting cytokinesis through activation of the SIN pathway.
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232.
authors.forename: Nicole
authors.initials: N
authors.lastname: Rachfall
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232.
authors.forename: Alyssa E
authors.initials: AE
authors.lastname: Johnson
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232.
authors.forename: Sapna
authors.initials: S
authors.lastname: Mehta
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232.
authors.forename: Jun-Song
authors.initials: JS
authors.lastname: Chen
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232 kathy.gould@vanderbilt.edu.
authors.forename: Kathleen L
authors.initials: KL
authors.lastname: Gould
mesh_terms: D016203:CDC2 Protein Kinase / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D048749:Cytokinesis; D008677:Metaphase; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D012568:Schizosaccharomyces / Q000166:cytology / Q000201:enzymology*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism; D015398:Signal Transduction; D064048:Spindle Pole Bodies
chemical_list: C100413:Byr4 protein, S pombe; D018797:Cell Cycle Proteins; D012097:Repressor Proteins; D029702:Schizosaccharomyces pombe Proteins; C501407:Plo1 protein, S pombe; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase