A role for PP1 in the Cdc2/cyclin B-mediated positive feedback activation of Cdc25

Seth S. Margolis, Jennifer A. Perry, Douglas H. Weitzel, Christopher D. Freel, Minoru Yoshida, Timothy A. Haystead, Sally Kornbluth

Research output: Contribution to journalArticlepeer-review

75 Scopus citations


The Cdc25 phosphatase promotes entry into mitosis through the removal of inhibitory phosphorylations on the Cdc2 subunit of the Cdc2/CyclinB complex. During interphase, or after DNA damage, Cdc25 is suppressed by phosphorylation at Ser287 (Xenopus numbering; Ser216 of human Cdc25C) and subsequent binding of the small acidic protein, 14-3-3. As reported recently, at the time of mitotic entry, 14-3-3 protein is removed from Cdc25 and S287 is dephosphorylated by protein phosphatase 1 (PP1). After the initial activation of Cdc25 and consequent derepression of Cdc2/CyclinB, Cdc25 is further activated through a Cdc2-catalyzed positive feedback loop. Although the existence of such a loop has been appreciated for some time, the molecular mechanism for this activation has not been described. We report here that phosphorylation of S285 by Cdc2 greatly enhances recruitment of PP1 to Cdc25, thereby accelerating S287 dephosphorylation and mitotic entry. Moreover, we show that two other previously reported sites of Cdc2-catalyzed phosphorylation on Cdc25 are required for maximal biological activity of Cdc25, but they do not contribute to PP1 regulation and do not act solely through controlling S287 phosphorylation. Therefore, multiple mechanisms, including enhanced recruitment of PP1, are used to promote full activation of Cdc25 at the time of mitotic entry.

Original languageEnglish (US)
Pages (from-to)1779-1789
Number of pages11
JournalMolecular biology of the cell
Issue number4
StatePublished - Apr 2006
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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