title: A New Membrane Protein Sbg1 Links the Contractile Ring Apparatus and Septum Synthesis Machinery in Fission Yeast.
abstract: Cytokinesis in many organisms requires a plasma membrane anchored actomyosin ring, whose contraction facilitates cell division. In yeast and fungi, actomyosin ring constriction is also coordinated with division septum assembly. How the actomyosin ring interacts with the plasma membrane and the plasma membrane-localized septum synthesizing machinery remains poorly understood. In Schizosaccharomyces pombe, an attractive model organism to study cytokinesis, the β-1,3-glucan synthase Cps1p / Bgs1p, an integral membrane protein, localizes to the plasma membrane overlying the actomyosin ring and is required for primary septum synthesis. Through a high-dosage suppressor screen we identified an essential gene, sbg1+ (suppressor of beta glucan synthase 1), which suppressed the colony formation defect of Bgs1-defective cps1-191 mutant at higher temperatures. Sbg1p, an integral membrane protein, localizes to the cell ends and to the division site. Sbg1p and Bgs1p physically interact and are dependent on each other to localize to the division site. Loss of Sbg1p results in an unstable actomyosin ring that unravels and slides, leading to an inability to deposit a single contiguous division septum and an important reduction of the β-1,3-glucan proportion in the cell wall, coincident with that observed in the cps1-191 mutant. Sbg1p shows genetic and / or physical interaction with Rga7p, Imp2p, Cdc15p, and Pxl1p, proteins known to be required for actomyosin ring integrity and efficient septum synthesis. This study establishes Sbg1p as a key member of a group of proteins that link the plasma membrane, the actomyosin ring, and the division septum assembly machinery in fission yeast.
authors.affiliation: Temasek Life Sciences Laboratory, National University of Singapore, 1 Research Link, Singapore.|Department of Biological Sciences, National University of Singapore, Singapore.
authors.forename: Kriti
authors.initials: K
authors.lastname: Sethi
authors.affiliation: Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
authors.forename: Saravanan
authors.initials: S
authors.lastname: Palani
authors.affiliation: Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Cinetificas/Universidad de Salamanca, Salamanca, Spain.
authors.forename: Juan C G
authors.initials: JC
authors.lastname: Cortés
authors.affiliation: Laboratory of Electron Microscopy/Bio-imaging Centre, and Department of Chemical and Biological Sciences, Faculty of Sciences, Japan Women's University, Mejirodai, Bunkyo-ku, Tokyo, Japan.
authors.forename: Mamiko
authors.initials: M
authors.lastname: Sato
authors.affiliation: Temasek Life Sciences Laboratory, National University of Singapore, 1 Research Link, Singapore.
authors.forename: Mayalagu
authors.initials: M
authors.lastname: Sevugan
authors.affiliation: Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Cinetificas/Universidad de Salamanca, Salamanca, Spain.
authors.forename: Mariona
authors.initials: M
authors.lastname: Ramos
authors.affiliation: Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
authors.forename: Shruthi
authors.initials: S
authors.lastname: Vijaykumar
authors.affiliation: Laboratory of Electron Microscopy/Bio-imaging Centre, and Department of Chemical and Biological Sciences, Faculty of Sciences, Japan Women's University, Mejirodai, Bunkyo-ku, Tokyo, Japan.|NPO Integrated Imaging Research Support, Hirakawa-cho, Chiyoda-ku, Tokyo, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Osumi
authors.affiliation: Temasek Life Sciences Laboratory, National University of Singapore, 1 Research Link, Singapore.|Department of Biological Sciences, National University of Singapore, Singapore.
authors.forename: Naweed I
authors.initials: NI
authors.lastname: Naqvi
authors.affiliation: Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Cinetificas/Universidad de Salamanca, Salamanca, Spain.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Ribas
authors.affiliation: Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
authors.forename: Mohan
authors.initials: M
authors.lastname: Balasubramanian
mesh_terms: D008841:Actin Cytoskeleton / Q000235:genetics; D000205:Actomyosin / Q000235:genetics* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics; D002455:Cell Division / Q000235:genetics; D002462:Cell Membrane; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D048749:Cytokinesis / Q000235:genetics*; D005964:Glucosyltransferases / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics*; D012568:Schizosaccharomyces / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics* / Q000378:metabolism; D047071:beta-Glucans / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D008565:Membrane Proteins; C000618219:Sbg1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D047071:beta-Glucans; D000205:Actomyosin; C033363:beta-1,3-glucan; D005964:Glucosyltransferases; C020570:1,3-beta-glucan synthase