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Updated: Feb 27, 2026

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

Published on: May 3, 2018

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Structural basis of divergent cyclin-dependent kinase activation by Spy1/RINGO proteins

Denise A McGrath1, Bre-Anne Fifield2, Aimee H Marceau1

  • 1Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA, USA.

The EMBO Journal
|July 2, 2017
PubMed

Insights

Spy1 proteins activate cyclin-dependent kinases (Cdks) in cancer cells, driving proliferation. Structural analysis reveals Spy1’s unique mechanism, offering new therapeutic targets for cancer treatment.

Area of Science:

  • Molecular Biology
  • Structural Biology
  • Cancer Research

Background:

  • Cyclin-dependent kinases (Cdks) regulate cell division but are often dysregulated in cancer.
  • Spy1/RINGO (Spy1) proteins activate Cdks but evade normal cell-cycle control.
  • The mechanism by which Spy1 activates Cdks and its role in cancer proliferation are poorly understood.

Purpose of the Study:

  • To elucidate the structural mechanism by which Spy1 activates Cdk2.
  • To understand why Spy1-Cdk complexes are resistant to inhibition by p27.
  • To identify potential therapeutic strategies targeting Spy1 in cancer.

Main Methods:

  • X-ray crystallography to determine the structures of Cdk2-Spy1 and p27-Cdk2-Spy1 complexes.
  • Site-directed mutagenesis to identify key residues in Spy1 function.
  • Cell proliferation assays to assess the impact of Spy1 mutations.

Main Results:

  • Spy1 binding induces structural changes in Cdk2, bypassing the need for activation loop phosphorylation.
  • Spy1 lacks a cyclin-binding site, explaining its resistance to p27 inhibition and lack of substrate specificity.
  • Mutations in Spy1 were identified that abolish Cdk2 activation and cellular proliferation.

Conclusions:

  • Spy1 activates Cdk2 through a unique mechanism involving structural remodeling.
  • The structural insights into Spy1-Cdk interactions provide a basis for developing targeted cancer therapies.
  • Targeting Spy1 offers a promising strategy to inhibit aberrant proliferation in cancers that overexpress Spy1.
Keywords:
Cdkcell cyclekinase inhibitorsp27protein phosphorylation

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