PI 3-kinase-dependent phosphorylation of Plk1-Ser99 promotes association with 14-3-3γ and is required for metaphase-anaphase transition

Nat Commun. 2013;4:1882. doi: 10.1038/ncomms2879.


Polo-like kinase 1 (Plk1) controls multiple aspects of mitosis and is activated through its phosphorylation at Thr210. Here we identify Ser99 on Plk1 as a novel mitosis-specific phosphorylation site, which operates independently of Plk1-Thr210 phosphorylation. Plk1-Ser99 phosphorylation creates a docking site for 14-3-3γ, and this interaction stimulates the catalytic activity of Plk1. Knockdown of 14-3-3γ or replacement of wild-type (WT) Plk1 by a Ser99-phospho-blocking mutant leads to a prometaphase/metaphase-like arrest due to the activation of the spindle assembly checkpoint. Inhibition of phosphatidylinositol 3-kinase (PI3K) and Akt significantly reduces the level of Plk1-Ser99 phosphorylation and delays metaphase to anaphase transition. Plk1-Ser99 phosphorylation requires not only Akt activity but also protein(s) associated with Plk1 in a mitosis-specific manner. Therefore, mitotic Plk1 activity is regulated not only by Plk1-Thr210 phosphorylation, but also by Plk1 binding to 14-3-3γ following Plk1-Ser99 phosphorylation downstream of the PI3K-Akt signalling pathway. This novel Plk1 activation pathway controls proper progression from metaphase to anaphase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 14-3-3 Proteins / metabolism*
  • Anaphase*
  • Animals
  • Biocatalysis
  • Caenorhabditis elegans
  • Cell Cycle Proteins / metabolism*
  • Drosophila melanogaster
  • Enzyme Activation
  • HeLa Cells
  • Humans
  • M Phase Cell Cycle Checkpoints
  • Metaphase*
  • Models, Biological
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphoinositide-3 Kinase Inhibitors
  • Phosphorylation
  • Phosphoserine / metabolism*
  • Protein Binding
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt / metabolism
  • Signal Transduction


  • 14-3-3 Proteins
  • Cell Cycle Proteins
  • Phosphoinositide-3 Kinase Inhibitors
  • Proto-Oncogene Proteins
  • Phosphoserine
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • polo-like kinase 1