The PolySUMOylation Axis Promotes Nucleolar Release of Tof2 for Mitotic Exit

Nucleolar proteins Tof2, Net1, and Fob1 are required for this sequestration. Although it is known that these nucleolar proteins are SUMOylated, how SUMOylation regulates their activity remains unknown.

Here, we show that Tof2 exhibits cell cycle-regulated nucleolar delocalization and turnover. Depletion of nuclear SUMO protease Ulp2 not only causes Tof2 polySUMOylation, nucleolar delocalization, and degradation, but also leads to Cdc14 nucleolar release and activation. This outcome depends on polySUMOylation and the activity of downstream enzymes SUMO-targeted ubiquitin ligase and Cdc48/p97 segregase.