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Updated: Jul 11, 2026

Analysis of Cell Cycle Position in Mammalian Cells
12:19

Analysis of Cell Cycle Position in Mammalian Cells

Published on: January 21, 2012

Structural basis of inhibition of CDK-cyclin complexes by INK4 inhibitors

P D Jeffrey1, L Tong, N P Pavletich

  • 1Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.

Genes & Development
|December 22, 2000
PubMed

Insights

The crystal structure of an inactive Cdk6-p18(INK4c)-cyclin complex reveals how INK4 inhibitors block cell cycle progression. This provides insights into cyclin-dependent kinase regulation and cancer. Keywords: Cdk4/6, cell cycle, cancer, INK4 inhibitors, crystal structure.

Area of Science:

  • Molecular Biology
  • Structural Biology
  • Biochemistry

Background:

  • Cyclin-dependent kinases 4 and 6 (Cdk4/6) control cell cycle G1 progression and are crucial for cell proliferation.
  • Deregulation of CDKs is common in cancer, making them targets for therapeutic intervention.
  • INK4 proteins are key inhibitors of CDK4/6 activity, regulating their function through binding interactions.

Purpose of the Study:

  • To elucidate the structural mechanism by which INK4 inhibitors inactivate Cdk4/6-cyclin complexes.
  • To provide atomic-level insights into the interaction between Cdk6, p18(INK4c), and a D-type cyclin.
  • To understand the specificity of D-type cyclins for Cdk4/6.

Main Methods:

  • X-ray crystallography was used to determine the 2.9-Å resolution structure of the ternary complex.
  • Biochemical assays were implied to study the binding interactions and inhibitory mechanisms.

Main Results:

  • The crystal structure reveals that p18(INK4c) inhibits Cdk6 by distorting the ATP binding site and misaligning catalytic residues.
  • p18(INK4c) also alters the cyclin binding site, reducing the interface size and weakening cyclin affinity.
  • The findings support a model where INK4 binding promotes cyclin dissociation from the CDK.

Conclusions:

  • The structure provides a detailed molecular understanding of INK4-mediated inhibition of Cdk4/6.
  • This work sheds light on the regulation of the cell cycle and offers potential avenues for cancer therapy development.
  • Insights into D-type cyclin specificity for Cdk4/6 are provided.

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