title: Cell wall remodeling at the fission yeast cell division site requires the Rho-GEF Rgf3p.
abstract: Cytokinesis in Schizosaccharomyces pombe is accompanied by several stages of cell wall remodeling at the division site. Coincident with actomyosin ring constriction, primary and secondary septa are deposited and then the primary septum is degraded to release daughter cells from one another. These steps require the activities of glucan synthases and glucanases, respectively, which must be coordinated with one another to prevent cell lysis. The lad1-1 mutation undergoes cell lysis specifically at cell division owing to the absence of the Rgf3p Rho1-guanine nucleotide exchange factor (GEF) at the division site. Electron microscopic analysis indicates that lysis occurs only as the primary septum begins to be degraded. Overproduction of either Rho1p or the previously uncharacterized Rab-GTPase-activating protein (GAP) involved in secretion, Gyp10p, suppresses lad1-1 lethality. Rgf3p is periodically produced in an Ace2p-dependent manner and localizes to the medial region of the cell early in mitosis, a pattern of expression distinct from the highly related Rho-GEF, Rgf1p. Although rgf1+ is not an essential gene, it is synthetically lethal with rgf2-deleted cells whereas no negative genetic interactions were detected between rgf2-deleted cells and lad1-1. Our data suggest that the three closely related fission yeast Rho-GEF molecules perform two distinct essential functions. Rgf3p appears necessary to stimulate Rho1p-mediated activation of a glucan synthase crucial after septation for proper new cell-end formation.
authors.affiliation: Howard Hughes Medical Institute and Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Morrell-Falvey
authors.forename: Liping
authors.initials: L
authors.lastname: Ren
authors.forename: Anna
authors.initials: A
authors.lastname: Feoktistova
authors.forename: Greg Den
authors.initials: GD
authors.lastname: Haese
authors.forename: Kathleen L
authors.initials: KL
authors.lastname: Gould
mesh_terms: D002455:Cell Division / Q000502:physiology; D002473:Cell Wall / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D012568:Schizosaccharomyces / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; C502214:Rgf3 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D020741:rho GTP-Binding Proteins; C511156:rho1 protein, S pombe