title: A PP2A-B55 recognition signal controls substrate dephosphorylation kinetics during mitotic exit.
abstract: PP2A-B55 is one of the major phosphatases regulating cell division. Despite its importance for temporal control during mitotic exit, how B55 substrates are recognized and differentially dephosphorylated is unclear. Using phosphoproteomics combined with kinetic modeling to extract B55-dependent rate constants, we have systematically identified B55 substrates and assigned their temporal order in mitotic exit. These substrates share a bipartite polybasic recognition determinant (BPR) flanking a Cdk1 phosphorylation site. Experiments and modeling show that dephosphorylation rate is encoded into B55 substrates, including its inhibitor ENSA, by cooperative action of basic residues within the BPR. A complementary acidic surface on B55 decodes this signal, supporting a cooperative electrostatic mechanism for substrate selection. A further level of specificity is encoded into B55 substrates because B55 displays selectivity for phosphothreonine. These simple biochemical properties, combined with feedback control of B55 activity by the phosphoserine-containing substrate/inhibitor ENSA, can help explain the temporal sequence of events during exit from mitosis.
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Cundell
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK.
authors.forename: Lukas H
authors.identifier: 0000-0002-3888-8231
authors.initials: LH
authors.lastname: Hutter
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK.
authors.forename: Ricardo
authors.identifier: 0000-0002-7328-0977
authors.initials: R
authors.lastname: Nunes Bastos
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK.
authors.forename: Elena
authors.identifier: 0000-0001-5279-2677
authors.initials: E
authors.lastname: Poser
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK.
authors.forename: James
authors.initials: J
authors.lastname: Holder
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK Department of Chemistry, University of Oxford, Oxford OX1 3TA, England, UK.
authors.forename: Shabaz
authors.identifier: 0000-0003-2640-9560
authors.initials: S
authors.lastname: Mohammed
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK.
authors.forename: Bela
authors.identifier: 0000-0002-6961-1366
authors.initials: B
authors.lastname: Novak
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK francis.barr@bioch.ox.ac.uk.
authors.forename: Francis A
authors.identifier: 0000-0001-7518-253X
authors.initials: FA
authors.lastname: Barr
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D000705:Anaphase / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008938:Mitosis / Q000187:drug effects; D022022:Nuclear Pore / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000737:chemistry / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D055672:Static Electricity; D013379:Substrate Specificity / Q000187:drug effects; D013997:Time Factors
chemical_list: D000596:Amino Acids; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; C079377:NUP153 protein, human; D028861:Nuclear Pore Complex Proteins; C116662:PRC1 protein, human; D021122:Protein Subunits; D054648:Protein Phosphatase 2