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Rho1 Directs Formin-Mediated Actin Ring Assembly during Budding Yeast Cytokinesis

2002; Elsevier BV; Volume: 12; Issue: 21 Linguagem: Inglês

10.1016/s0960-9822(02)01238-1

1879-0445

Nicola Tolliday, Lynn VerPlank, Rong Li,

Cellular transport and secretion

In eukaryotic cells, dynamic rearrangement of the actin cytoskeleton is critical for cell division. In the yeast Saccharomyces cerevisiae, three main structures constitute the actin cytoskeleton: cortical actin patches, cytoplasmic actin cables, and the actin-based cytokinetic ring [1Pruyne D. Bretscher A. Polarization of cell growth in yeast.J. Cell Sci. 2000; 113: 571-585Crossref PubMed Google Scholar, 2Adams A.E.M. Pringle J.R. Relationship of actin and tubulin distribution to bud growth in wild-type and morphogenetic mutant Saccharomyces cerevisiae.J. Cell Biol. 1984; 98: 934-945Crossref PubMed Scopus (587) Google Scholar, 3Lippincott J. Li R. Sequential assembly of myosin II, an IQGAP-like protein, and filamentous actin, to a ring structure involved in budding yeast cytokinesis.J. Cell Biol. 1998; 140: 355-366Crossref PubMed Scopus (301) Google Scholar, 4Bi E. Maddox P. Lew D.J. Salmon E.D. McMillan J.N. Yeh E. Pringle J.R. Involvement of an actomyosin contractile ring in Saccharomyces cerevisiae cytokinesis.J. Cell Biol. 1998; 142: 1301-1312Crossref PubMed Scopus (330) Google Scholar]. The conserved Arp2/3 complex and a WASP-family protein mediate actin patch formation, whereas the yeast formins (Bni1 and Bnr1) promote assembly of actin cables [5Li R. Bee1, a yeast protein with homology to Wiskott-Aldrich syndrome protein, is critical for the assembly of cortical actin cytoskeleton.J. Cell Biol. 1997; 136: 649-658Crossref PubMed Scopus (218) Google Scholar, 6Winter D. Podtelejnikov A.V. Mann M. Li R. The complex containing actin-related proteins Arp2 and Arp3 is required for the motility and integrity of yeast actin patches.Curr. Biol. 1997; 7: 519-529Abstract Full Text Full Text PDF PubMed Scopus (199) Google Scholar, 7Winter D. Lechler T. Li R. Activation of the yeast Arp2/3 complex by Bee1p, a WASP-family protein.Curr. Biol. 1999; 9: 501-504Abstract Full Text Full Text PDF PubMed Scopus (189) Google Scholar, 8Sagot I. Klee S.K. Pellman D. Yeast formins regulate cell polarity by controlling the assembly of actin cables.Nat. Cell Biol. 2002; 4: 42-50Crossref PubMed Scopus (319) Google Scholar, 9Evangelista M. Pruyne D. Amberg D.C. Boone C. Bretscher A. Formins direct Arp2/3-independent actin filament assembly to polarize cell growth in yeast.Nat. Cell Biol. 2002; 4: 32-41Crossref PubMed Scopus (163) Google Scholar]. However, the mechanism of actin ring formation is currently unclear. Here, we show that actin filaments are required for cytokinesis in S. cerevisiae, and that the actin ring is a highly dynamic structure that undergoes constant turnover. Assembly of the actin ring requires the formin-like proteins and profilin, but is not Arp2/3-mediated. Furthermore, the formin-dependent actin ring assembly pathway is regulated by the Rho-type GTPase Rho1 but not Cdc42. Finally, we show that the formins are not required for localization of Cyk1/Iqg1, an IQGAP-like protein previously shown to be required for actin ring formation, suggesting that formin-like proteins and Cyk1 act synergistically but independently in assembly of the actin ring.