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Biological Chemistry

Editor-in-Chief: Brüne, Bernhard

Editorial Board Member: Buchner, Johannes / Ludwig, Stephan / Sies, Helmut / Turk, Boris / Wittinghofer, Alfred

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Evidence that a septin diffusion barrier is dispensable for cytokinesis in budding yeast

Carsten Wloka1, 2, a / Ryuichi Nishihama3, a / Masayuki Onishi3 / Younghoon Oh1 / Julia Hanna1 / John R. Pringle3 / Michael Krauß2 / 1

1Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058, USA

2Institute of Chemistry and Biochemistry, Department of Membrane Biochemistry, Freie Universität Berlin, Takustraße 6, D-14195 Berlin, Germany

3Department of Genetics, Stanford University of School of Medicine, Stanford, CA 94305, USA

aThese authors contributed equally to this work.

Corresponding author

Citation Information: Biological Chemistry. Volume 392, Issue 8-9, Pages 813–829, ISSN (Online) 1437-4315, ISSN (Print) 1431-6730, DOI: 10.1515/BC.2011.083, August 2011

Publication History

Received:
2011-05-08
Accepted:
2011-06-22

Abstract

Septins are essential for cytokinesis in Saccharomyces cerevisiae, but their precise roles remain elusive. Currently, it is thought that before cytokinesis, the hourglass-shaped septin structure at the mother-bud neck acts as a scaffold for assembly of the actomyosin ring (AMR) and other cytokinesis factors. At the onset of cytokinesis, the septin hourglass splits to form a double ring that sandwiches the AMR and may function as diffusion barriers to restrict diffusible cytokinesis factors to the division site. Here, we show that in cells lacking the septin Cdc10 or the septin-associated protein Bud4, the septins form a ring-like structure at the mother-bud neck that fails to re-arrange into a double ring early in cytokinesis. Strikingly, AMR assembly and constriction, the localization of membrane-trafficking and extracellular-matrix-remodeling factors, cytokinesis, and cell-wall-septum formation all occur efficiently in cdc10Δ and bud4Δ mutants. Thus, diffusion barriers formed by the septin double ring do not appear to be critical for S. cerevisiae cytokinesis. However, an AMR mutation and a septin mutation have synergistic effects on cytokinesis and the localization of cytokinesis proteins, suggesting that tethering to the AMR and a septin diffusion barrier may function redundantly to localize proteins to the division site.

Keywords: Bud4; chitin synthase; exocyst; membrane-trafficking; septum formation; W303

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