Role for the PP2A/B56delta phosphatase in regulating 14-3-3 release from Cdc25 to control mitosis.
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.
Margolis
Seth S
SS
Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
Perry
Jennifer A
JA
Forester
Craig M
CM
Nutt
Leta K
LK
Guo
Yanxiang
Y
Jardim
Melanie J
MJ
Thomenius
Michael J
MJ
Freel
Christopher D
CD
Darbandi
Rashid
R
Ahn
Jung-Hyuck
JH
Arroyo
Jason D
JD
Wang
Xiao-Fan
XF
Shenolikar
Shirish
S
Nairn
Angus C
AC
Dunphy
William G
WG
Hahn
William C
WC
Virshup
David M
DM
Kornbluth
Sally
S
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*
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