Multisite Phosphorylation of the Guanine Nucleotide Exchange Factor Cdc24 during Yeast Cell Polarization

Abstract

Cell polarization is the process by which cells establish asymmetry along a single axis and is essential for processes such as cell migration and asymmetric cell division [1]. Budding yeast is an excellent model for the study of cell polarity, because it divides asymmetrically between the mother and bud and displays a characteristic cell and actin morphology at each cell cycle stage, facilitating the study of different polarity states [2]. Also, many proteins involved in cell polarity, such as the Rho GTPase Cdc42, are conserved from yeast to mammals [3], [4], [5]. Yeast cells are round and unpolarized in G1 phase, but after the G1-S transition, the actin cytoskeleton and localization of the Cdc42 GTPase are polarized to the presumptive bud site [2]. The cell is then set up for bud emergence, which occurs shortly afterwards. Bud formation through polarized growth is required for successful cell division.