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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
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Characterization of a new family of cyclin-dependent kinase activators

Ana Dinarina1, Laurent H Perez, Amparo Davila

  • 1European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.

The Biochemical Journal
|December 3, 2004
PubMed

Insights

Researchers discovered a new family of mammalian RINGO proteins that activate cyclin-dependent kinases (CDKs). These RINGO proteins regulate cell cycle progression and may offer insights into cyclin-independent kinase functions.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Cell cycle progression is tightly regulated by cyclin-dependent kinases (CDKs) and their activating partners, cyclins.
  • Xenopus RINGO protein was previously identified as a cyclin-like activator of CDK1 and CDK2, crucial for meiotic cell cycle regulation in oocytes.

Purpose of the Study:

  • To characterize mammalian RINGO proteins and elucidate their role in CDK activation and cell cycle regulation.
  • To investigate the interaction between RINGO proteins, CDKs (CDK1, CDK2, CDK4, CDK6), and the CDK inhibitor p27Kip1.

Main Methods:

  • Sequence analysis to compare mammalian and Xenopus RINGO proteins.
  • In vitro binding and kinase assays to assess the interaction and activation of CDKs by RINGO proteins.
  • Identification of critical residues in RINGO and CDK2 involved in their interaction.

Main Results:

  • Four mammalian RINGO proteins were identified, sharing significant sequence identity with Xenopus RINGO in a conserved core region.
  • All characterized RINGO proteins bind and activate CDK1 and CDK2, but not CDK4 or CDK6, with varying efficiencies.
  • The conserved core sequence of RINGO is essential for CDK activation, and specific CDK2 residues are critical for RINGO binding.
  • RINGO proteins bind to p27Kip1 with an efficiency inversely proportional to their CDK1 binding ability.

Conclusions:

  • A novel family of mammalian RINGO proteins capable of activating CDK1 and CDK2 has been identified.
  • These RINGO proteins represent potential regulators of the cell cycle.
  • The findings suggest possible cyclin-independent functions for CDK1 and CDK2 mediated by RINGO proteins.

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