Using the budding yeast Saccharomyces cerevisiae as a model system, these two evolutionarily conserved processes have been studied with a combination of genetic, cytological, molecular biological, and biochemical approaches.
Cell polarization is essential for development and differentiation.
Cdc42p, a small Rho-like GTPase, plays a major role in the polarized organization of actin cytoskeleton in many biological systems ranging from yeast to human. Malfunctioning of Cdc42p signaling pathway can lead to disorganized actin cytoskeleton and is associated with serious human diseases such as cancer and Wiskott-Aldrich syndrome. However, the effector pathway linking Cdc42p to the actin cytoskeleton remains largely unknown. Interestingly, they also have homologues from many organisms including the human oncogene tre17 . Consistent with this hypothesis is that the localization pattern of MSB3p or MSB4p parallels that of Cdc42p in the cell cycle, and their localization depends on Cdc42p function.