Cyclin-dependent kinase (CDK) phosphorylation destabilizes somatic Wee1 via multiple pathways

Proc Natl Acad Sci U S A. 2005 Aug 16;102(33):11663-8. doi: 10.1073/pnas.0500410102. Epub 2005 Aug 5.

Abstract

At the onset of M phase, the activity of somatic Wee1 (Wee1A), the inhibitory kinase for cyclin-dependent kinase (CDK), is down-regulated primarily through proteasome-dependent degradation after ubiquitination by the E3 ubiquitin ligase SCF(beta-TrCP). The F-box protein beta-TrCP (beta-transducin repeat-containing protein), the substrate recognition component of the ubiquitin ligase, binds to its substrates through a conserved binding motif (phosphodegron) containing two phosphoserines, DpSGXXpS. Although Wee1A lacks this motif, phosphorylation of serines 53 and 123 (S53 and S123) of Wee1A by polo-like kinase 1 (Plk1) and CDK, respectively, are required for binding to beta-TrCP. The sequence surrounding phosphorylated S53 (DpSAFQE) is similar to the conserved beta-TrCP-binding motif; however, the role of S123 phosphorylation (EEGFGSSpSPVK) in beta-TrCP binding was not elucidated. In the present study, we show that phosphorylation of S123 (pS123) by CDK promoted the binding of Wee1A to beta-TrCP through three independent mechanisms. The pS123 not only directly interacted with basic residues in the WD40 repeat domain of beta-TrCP but also primed phosphorylation by two independent protein kinases, Plk1 and CK2 (formerly casein kinase 2), to create two phosphodegrons on Wee1A. In the case of Plk1, S123 phosphorylation created a polo box domain-binding motif (SpSP) on Wee1A to accelerate phosphorylation of S53 by Plk1. CK2 could phosphorylate S121, but only if S123 was phosphorylated first, thereby generating the second beta-TrCP-binding site (EEGFGpS121). Using a specific inhibitor of CK2, we showed that the phosphorylation-dependent degradation of Wee1A is important for the proper onset of mitosis.

MeSH terms

  • Amino Acid Sequence
  • Binding Sites
  • Casein Kinase II / antagonists & inhibitors
  • Casein Kinase II / metabolism
  • Cell Cycle
  • Cell Cycle Proteins / metabolism
  • Cell Line
  • Cyclin-Dependent Kinases / metabolism*
  • Humans
  • Mitosis
  • Models, Molecular
  • Molecular Sequence Data
  • Phosphorylation
  • Phosphoserine / metabolism
  • Protein Binding
  • Protein Kinases / metabolism
  • Protein Structure, Tertiary
  • Protein-Serine-Threonine Kinases
  • Protein-Tyrosine Kinases / chemistry
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism
  • Sequence Alignment
  • Signal Transduction*
  • beta-Transducin Repeat-Containing Proteins / chemistry
  • beta-Transducin Repeat-Containing Proteins / metabolism

Substances

  • Cell Cycle Proteins
  • Proto-Oncogene Proteins
  • beta-Transducin Repeat-Containing Proteins
  • Phosphoserine
  • Protein Kinases
  • Protein-Tyrosine Kinases
  • Casein Kinase II
  • Protein-Serine-Threonine Kinases
  • polo-like kinase 1
  • Cyclin-Dependent Kinases