Ras and the Rho Effector Cla4 Collaborate to Target and Anchor Lte1 at the Bud Cortex

Abstract

Lte1, a protein important for exit from mitosis, localizes to the bud cortex as soon as the bud forms and remains there until cells exit from mitosis. Ras, the Rho GTPase Cdc42 and its effector the protein kinase Cla4 are required for Lte1’s association with the bud cortex. Here we investigate how Ras, and the Cdc42 effector Cla4 regulate the localization of Lte1. We find that Ras2 and Lte1 associate in stages of the cell cycle when Lte1 is phosphorylated and associated with the bud cortex and that this association requires CLA4. Additionally, RAS1 and RAS2 are required for CLA4-dependent Lte1 phosphorylation. Our findings suggest that Cla4-dependent phosphorylation promotes the initial association of Lte1 with Ras at the bud cortex and that Ras is required to stabilize phosphorylated forms of Lte1 at the bud cortex. Our results also raise the interesting possibility that the localization of Lte1 affects the protein’s ability to promote mitotic exit.