Exit from Mitosis Is Triggered by Tem1-Dependent Release of the Protein Phosphatase Cdc14 from Nucleolar RENT Complex

Abstract

Exit from mitosis in budding yeast requires a group of essential proteins--including the GTPase Tem1 and the protein phosphatase Cdc14--that downregulate cyclin-dependent kinase activity. We identified a mutation, net1-1, that bypasses the lethality of tem1 delta. NET1 encodes a novel protein, and mass spectrometric analysis reveals that it is a key component of a multifunctional complex, denoted RENT (for regulator of nucleolar silencing and telophase), that also contains Cdc14 and the silencing regulator Sir2. From G1 through anaphase, RENT localizes to the nucleolus, and Cdc14 activity is inhibited by Net1. In late anaphase, Cdc14 dissociates from RENT, disperses throughout the cell in a Tem1-dependent manner, and ultimately triggers mitotic exit. Nucleolar sequestration may be a general mechanism for the regulation of diverse biological processes.

The Role of the Polo Kinase Cdc5 in Controlling Cdc14 Localization

“…Under these conditions, cells arrested in telophase with Cdc14 sequestered in the nucleolus ( Figure 1C). Furthermore, the telophase arrest of Cdc5-depeleted cells was bypassed by the TAB6-1 mutation, a dominant allele of CDC14 (Supplemental Figure 3; Shou et al, 1999), indicating that promoting Cdc14 release from the nucleolus is CDC5's essential function during exit from mitosis.…”

“…In the budding yeast Saccharomyces cerevisiae, the protein phosphatase Cdc14 triggers this transition by reversing cyclin-dependent kinase (CDK) phosphorylation (reviewed in (Morgan, 1999;Bardin and Amon, 2001;McCollum and Gould, 2001). The activity of Cdc14 is controlled by Cfi1/Net1, which functions as a competitive inhibitor of this protein phosphatase (Shou et al, 1999;Visintin et al, 1999;Traverso et al, 2001). The association of Cdc14 with its inhibitor is cell cycle regulated.…”

“…The association of Cdc14 with its inhibitor is cell cycle regulated. During G1, S phase, G2, and metaphase Cfi1/ Net1 sequesters and inhibits Cdc14 in the nucleolus (Shou et al, 1999;Visintin et al, 1999). During anaphase the phosphatase dissociates from its inhibitor in the nucleolus and spreads throughout the cell, where it is presumably active and able to dephosphorylate its targets.…”

“…The Cdc Fourteen Early Anaphase Release (FEAR) network promotes release of Cdc14 from the nucleolus during early anaphase and the Mitotic Exit Network (MEN) maintains Cdc14 in this released state during late stages of anaphase and telophase (Shou et al, 1999;Visintin et al, 1999;Pereira et al, 2002;Stegmeier et al, 2002;. Inactivation of FEAR network components prevents Cdc14 release from the nucleolus during early anaphase, when the mitotic spindle is between 3 and 7 m in length.…”

SAC‐ing mitotic errors: How the spindle assembly checkpoint (SAC) plays defense against chromosome mis‐segregation

“…In budding yeast, Tem1p-GTP (the budding yeast homologue of the fission yeast Spg1p GTPase) triggers mitotic exit by promoting the release of the Cdc14p phosphatase from the nucleolus [Shou et al, 1999]. The released Cdc14p dephosphorylates Cdh1p and promotes APC/C-Cdh1p degradation of cyclin B and mitotic exit [Visintin et al, 1998].…”