Disappearance of Cdc14 from the daughter spindle pole body requires Glc7-Bud14

Abstract

Background/aim: The conserved phosphatase Cdc14 facilitates mitotic exit in budding yeast by counteracting mitotic cyclin-dependent kinase activity. Cdc14 is kept in the nucleolus until anaphase onset, when it is released transiently into the nucleoplasm. In late anaphase, Cdc14 is fully released into the cytoplasm upon activation of the mitotic exit network (MEN) to trigger mitotic exit. Cdc14 also localizes to yeast spindle pole bodies (SPBs) in anaphase and dephosphorylates key targets residing on SPBs to allow SPB duplication and prime the MEN. Protein phosphatase 1 (Glc7) with regulatory subunit Bud14 is another phosphatase that plays a key role in the spatiotemporal control of mitotic exit. In this study, we investigated the regulation of Cdc14 localization by Bud14-Glc7. Materials and methods: We used fluorescence microscopy to analyze Cdc14 localization in BUD14 wildtype and BUD14 knockout cells ( bud144 ) as well as in cells expressing a mutant allele of BUD14 ( bud14-F379A ) that cannot bind Glc7. We also utilized a yeast two- hybrid (Y2H) system to examine the interaction of Bud14 with Cdc14. Results: We found that Cdc14 remains at the SPBs longer in bud144 and bud14-F379A compared to wildtype cells. This effect is limited to the SPB that has migrated to the daughter cell (dSPB). Cdc14 localizes to both SPBs shortly after anaphase onset. In mid-to-late anaphase, levels of Cdc14 increase at the dSPB in both wildtype and bud144 cells. With mitotic exit, Cdc14 disappears from the dSPB in wildtype cells but not in bud144 cells. Accordingly, 50% of bud144 cells in G1 have Cdc14 at their SPBs. We also found that Cdc14 localization at the dSPB was largely, but not entirely, dependent on Bfa1 in bud144 cells. Furthermore, Bud14 interacted with Cdc14 in the Y2H system. Conclusion: Our results suggest that Glc7-Bud14 is part of a mechanism that promotes Cdc14 disappearance from the dSPB.