FIGURE 4: Model for biphasic Cdc42 polarization coupled to stepwise assembly of a new septin ring during axial budding. During T₁, two positive feedback loops likely operate: one involving Bud3 and Rsr1 (marked with red arrows and line); another involving Gic1/2 (marked with green arrows). The Bem1-mediated positive feedback loop likely operates during T₂ (gray lines and arrows). For simplicity, some other known links are omitted, including the link between the axial landmark and the Rsr1 GTPase module; and the link between Rsr1-GTP and Cdc24 (see text). Stepwise assembly of the septin ring in correlation with Cdc42 polarization during each temporal step in G1 is shown below: gray and blue rings denote old and new septin rings, respectively. Blue dots and gray dotted line denote newly recruited septin ‘clouds' and disassembling old ring, respectively. Modified from Refs. [61] and [21].

21. Miller KE, Lo WC, Chou CS, Park HO (2019). Temporal regulation of cell polarity via the interaction of the Ras GTPase Rsr1 and the scaffold protein Bem1. Mol Biol Cell 30(20): 2543-2557. 10.1091/mbc.E19-02-0106

61. Kang PJ, Miller KE, Guegueniat J, Beven L, Park H-O (2018). The shared role of the Rsr1 GTPase and Gic1/Gic2 in Cdc42 polarization. Mol Biol Cell 29(20): 2359-2369. 10.1091/mbc.E18-02-0145