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  • PP2A/B55 and Fcp1 regulate Greatwall and Ensa dephosphorylation during mitotic exit.

PP2A/B55 and Fcp1 regulate Greatwall and Ensa dephosphorylation during mitotic exit.

PLoS genetics (2014-01-07)
Nadia Hégarat, Clare Vesely, P K Vinod, Cory Ocasio, Nisha Peter, Julian Gannon, Antony W Oliver, Béla Novák, Helfrid Hochegger
ABSTRACT

Entry into mitosis is triggered by activation of Cdk1 and inactivation of its counteracting phosphatase PP2A/B55. Greatwall kinase inactivates PP2A/B55 via its substrates Ensa and ARPP19. Both Greatwall and Ensa/ARPP19 are regulated by phosphorylation, but the dynamic regulation of Greatwall activity and the phosphatases that control Greatwall kinase and its substrates are poorly understood. To address these questions we applied a combination of mathematical modelling and experiments using phospho-specific antibodies to monitor Greatwall, Ensa/ARPP19 and Cdk substrate phosphorylation during mitotic entry and exit. We demonstrate that PP2A/B55 is required for Gwl dephosphorylation at the essential Cdk site Thr194. Ensa/ARPP19 dephosphorylation is mediated by the RNA Polymerase II carboxy terminal domain phosphatase Fcp1. Surprisingly, inhibition or depletion of neither Fcp1 nor PP2A appears to block dephosphorylation of the bulk of mitotic Cdk1 substrates during mitotic exit. Taken together our results suggest a hierarchy of phosphatases coordinating Greatwall, Ensa/ARPP19 and Cdk substrate dephosphorylation during mitotic exit.

MATERIALS
Product Number
Brand
Product Description

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GeneJuice® Transfection Reagent, Non-lipid based chemical transfection reagent optimized for maximum transfection efficiency, ease-of-use, and minimal cytotoxicity on a wide variety of mammalian cells.
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Anti-Histone H3 Antibody, clone 6.6.2, clone 6.6.2, Upstate®, from mouse
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Anti-PP2A, C subunit antibody, Mouse monoclonal, clone 7A6, purified from hybridoma cell culture