Downregulation of the Tem1 GTPase by Amn1 after cytokinesis involves both nuclear import and SCF-mediated degradation.

At mitotic exit the cell cycle engine is reset to allow crucial processes, such as cytokinesis and replication origin licensing, to take place before a new cell cycle begins. In budding yeast, the cell cycle clock is reset by a Hippo-like kinase cascade called Mitotic Exit Network (MEN), whose activation is triggered at spindle pole bodies (SPBs) by the Tem1 GTPase. Yet, MEN activity must be extinguished once MEN-dependent processes have been accomplished. One factor contributing to switch off MEN is the Amn1 protein, which binds Tem1 and inhibits it through an unknown mechanism. Here, we show that Amn1 downregulates Tem1 through a dual mode. On one side, it evicts Tem1 from SPBs and escorts it into the nucleus. On the other, it promotes Tem1 degradation as part of an SCF ubiquitin ligase. Tem1 inhibition by Amn1 takes place after cytokinesis in the bud-derived daughter cell, consistent with its asymmetric appearance in the daughter versus the mother cell. This dual mechanism of Tem1 inhibition by Amn1 may contribute to rapidly extinguish MEN activity once it has fulfilled its functions.