TY - JOUR TI - Cell cycle entry triggers a switch between two modes of Cdc42 activation during yeast polarization AU - Witte, Kristen AU - Strickland, Devin AU - Glotzer, Michael A2 - McCormick, Sheila VL - 6 PY - 2017 DA - 2017/07/06 SP - e26722 C1 - eLife 2017;6:e26722 DO - 10.7554/eLife.26722 UR - https://doi.org/10.7554/eLife.26722 AB - Cell polarization underlies many cellular and organismal functions. The GTPase Cdc42 orchestrates polarization in many contexts. In budding yeast, polarization is associated with a focus of Cdc42•GTP which is thought to self sustain by recruiting a complex containing Cla4, a Cdc42-binding effector, Bem1, a scaffold, and Cdc24, a Cdc42 GEF. Using optogenetics, we probe yeast polarization and find that local recruitment of Cdc24 or Bem1 is sufficient to induce polarization by triggering self-sustaining Cdc42 activity. However, the response to these perturbations depends on the recruited molecule, the cell cycle stage, and existing polarization sites. Before cell cycle entry, recruitment of Cdc24, but not Bem1, induces a metastable pool of Cdc42 that is sustained by positive feedback. Upon Cdk1 activation, recruitment of either Cdc24 or Bem1 creates a stable site of polarization that induces budding and inhibits formation of competing sites. Local perturbations have therefore revealed unexpected features of polarity establishment. KW - optogenetics KW - Cdc42 KW - GTPase KW - Rho-family KW - cell signaling JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -