Phosphatase 1 Nuclear Targeting Subunit (PNUTS) Regulates Aurora Kinases and Mitotic Progression

Mitotic progression is regulated largely by reversible phosphorylation events that are mediated by mitotic kinases and phosphatases. Protein phosphatase 1 (PP1) has been shown to play a crucial role in regulation of mitotic entry, progression, and exit. We previously observed, in Xenopus egg extracts, that phosphatase 1 nuclear targeting subunit (PPP1R10/PNUTS) acts as a mitotic regulator by negatively modulating PP1. This study investigates the role of PNUTS in mitotic progression in mammalian cells, and demonstrates that PNUTS expression is elevated in mitosis and depletion partially blocks mitotic entry. Cells that enter mitosis after PNUTS knockdown exhibit frequent chromosome mis-segregation. Aurora A/B kinase complexes and several kinetochore components are identified as PNUTS-associated proteins. PNUTS depletion suppresses the activation of Aurora A/B kinases, and disrupts the spatiotemporal regulation of the chromosomal passenger complex (CPC). PNUTS dynamically localizes to kinetochores, and is required for the activation of the spindle assembly checkpoint. Finally, PNUTS depletion sensitizes the tumor cell response to Aurora inhibition, suggesting that PNUTS is a potential drug target in combination anticancer therapy. IMPLICATIONS: Delineation of how PNUTS governs the mitotic activation and function of Aurora kinases will improve the understanding of the complex phospho-regulation in mitotic progression, and suggest new options to enhance the therapeutic efficacy of Aurora inhibitors.