title: Role for the PP2A/B56delta phosphatase in regulating 14-3-3 release from Cdc25 to control mitosis.
abstract: DNA-responsive checkpoints prevent cell-cycle progression following DNA damage or replication inhibition. The mitotic activator Cdc25 is suppressed by checkpoints through inhibitory phosphorylation at Ser287 (Xenopus numbering) and docking of 14-3-3. Ser287 phosphorylation is a major locus of G2/M checkpoint control, although several checkpoint-independent kinases can phosphorylate this site. We reported previously that mitotic entry requires 14-3-3 removal and Ser287 dephosphorylation. We show here that DNA-responsive checkpoints also activate PP2A/B56delta phosphatase complexes to dephosphorylate Cdc25 at a site distinct from Ser287 (T138), the phosphorylation of which is required for 14-3-3 release. However, phosphorylation of T138 is not sufficient for 14-3-3 release from Cdc25. Our data suggest that creation of a 14-3-3 "sink," consisting of phosphorylated 14-3-3 binding intermediate filament proteins, including keratins, coupled with reduced Cdc25-14-3-3 affinity, contribute to Cdc25 activation. These observations identify PP2A/B56delta as a central checkpoint effector and suggest a mechanism for controlling 14-3-3 interactions to promote mitosis.
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Seth S
authors.initials: SS
authors.lastname: Margolis
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Perry
authors.forename: Craig M
authors.initials: CM
authors.lastname: Forester
authors.forename: Leta K
authors.initials: LK
authors.lastname: Nutt
authors.forename: Yanxiang
authors.initials: Y
authors.lastname: Guo
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Jardim
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Thomenius
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Freel
authors.forename: Rashid
authors.initials: R
authors.lastname: Darbandi
authors.forename: Jung-Hyuck
authors.initials: JH
authors.lastname: Ahn
authors.forename: Jason D
authors.initials: JD
authors.lastname: Arroyo
authors.forename: Xiao-Fan
authors.initials: XF
authors.lastname: Wang
authors.forename: Shirish
authors.initials: S
authors.lastname: Shenolikar
authors.forename: Angus C
authors.initials: AC
authors.lastname: Nairn
authors.forename: William G
authors.initials: WG
authors.lastname: Dunphy
authors.forename: William C
authors.initials: WC
authors.lastname: Hahn
authors.forename: David M
authors.initials: DM
authors.lastname: Virshup
authors.forename: Sally
authors.initials: S
authors.lastname: Kornbluth
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism*; D000818:Animals; D000071877:Checkpoint Kinase 1; D004261:DNA Replication; D004789:Enzyme Activation; D045325:HCT116 Cells; D006367:HeLa Cells; D020035:Holoenzymes / Q000378:metabolism; D006801:Humans; D007382:Intermediate Filaments / Q000378:metabolism; D007399:Interphase; D007633:Keratins / Q000378:metabolism; D008938:Mitosis; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D010769:Phosphothreonine / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D054648:Protein Phosphatase 2; D021122:Protein Subunits / Q000378:metabolism; D014981:Xenopus / Q000378:metabolism*; D029867:Xenopus Proteins / Q000378:metabolism*; D020687:cdc25 Phosphatases / Q000378:metabolism*
chemical_list: D048948:14-3-3 Proteins; D020035:Holoenzymes; D021122:Protein Subunits; D029867:Xenopus Proteins; D010769:Phosphothreonine; D007633:Keratins; D011494:Protein Kinases; D000071877:Checkpoint Kinase 1; C515682:B56delta phosphatase, Xenopus; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D020687:cdc25 Phosphatases