title: Rho1 directs formin-mediated actin ring assembly during budding yeast cytokinesis.
abstract: 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. 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. 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.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Nicola
authors.initials: N
authors.lastname: Tolliday
authors.forename: Lynn
authors.initials: L
authors.lastname: VerPlank
authors.forename: Rong
authors.initials: R
authors.lastname: Li
mesh_terms: D000199:Actins / Q000502:physiology*; D002453:Cell Cycle / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D020741:rho GTP-Binding Proteins / Q000502:physiology*
chemical_list: D000199:Actins; D029701:Saccharomyces cerevisiae Proteins; C051302:RHO1 protein, S cerevisiae; D020741:rho GTP-Binding Proteins