Related Experiment Video

Updated: Jun 25, 2026

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
12:26

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

Published on: May 3, 2018

The structure of CDK4/cyclin D3 has implications for models of CDK activation

T Takaki1, A Echalier, N R Brown

  • 1Cell Cycle Control Laboratory, Clare Hall Laboratories, London Research Institute, Blanche Lane, South Mimms, Herts EN6 3LD, United Kingdom.

Proceedings of the National Academy of Sciences of the United States of America
|February 25, 2009
PubMed

Insights

Cyclin-dependent kinase 4 (CDK4)/cyclin D3 activation requires more than just cyclin binding, differing from other CDK/cyclin complexes. Phosphorylation at T172 is crucial for CDK4/cyclin D3 kinase activity and regulation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Cyclin-dependent kinase 4 (CDK4)/cyclin D complexes regulate the G(1) phase of the cell cycle.
  • CDK4 phosphorylates the retinoblastoma gene product (pRb), promoting G(1) progression.

Purpose of the Study:

  • To elucidate the molecular pathway of CDK4 activation.
  • To understand CDK4 substrate selection.
  • To determine the structure of nonphosphorylated CDK4/cyclin D3.

Main Methods:

  • X-ray crystallography to determine the structure of nonphosphorylated CDK4/cyclin D3.
  • Biochemical assays to assess kinase activity and regulation.

Main Results:

  • The structure of nonphosphorylated CDK4/cyclin D3 reveals that cyclin binding alone does not fully activate the CDK active site.
  • Phosphorylated CDK4/cyclin D3 exhibits pRb kinase activity and is inhibited by p27(Kip1).
  • CDK4/cyclin D3, unlike CDK2/cyclin A, can be inactivated by lambda-phosphatase, indicating T172 phosphorylation accessibility.

Conclusions:

  • CDK4/cyclin D3 activation mechanism differs significantly from other known CDK/cyclin complexes.
  • Phosphorylation at T172 is essential for CDK4/cyclin D3 activity and regulation by phosphatases.

More Related Videos

Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors10:33

Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors

Published on: October 26, 2015

Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk113:15

Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1

Published on: February 25, 2016

Related Concept Videos

Positive Regulator Molecules02:39

Positive Regulator Molecules

Mitotic cell division results in daughter cells that exactly resemble the parent cell. However, errors in the DNA replication or distribution of genetic material may lead to genetic mutations that may be passed down to every new cell formed from the resulting abnormal cell. Propagation of such mutant cells is restricted through checkpoint mechanisms present at different stages of the cell cycle. These checkpoints involve regulator molecules that either promote or demote cell cycle events.
Positive Regulator Molecules01:45

Positive Regulator Molecules

To consistently produce healthy cells, the cell cycle—the process that generates daughter cells—must be precisely regulated.
Inhibition of Cdk Activity02:34

Inhibition of Cdk Activity

The orderly progression of the cell cycle depends on the activation of Cdk protein by binding to its cyclin partner. However, the cell cycle must be restricted when undergoing abnormal changes. Most cancers correlate to the deregulated cell cycle, and since Cdks are a central component of the cell cycle, Cdk inhibitors are extensively studied to develop anticancer agents. For instance, cyclin D associates with several Cdks, such as Cdk 4/6, to form an active complex. The cyclin D-Cdk4/6 complex...
Inhibition of CDK Activity02:34

Inhibition of CDK Activity

The orderly progression of the cell cycle depends on the activation of Cdk protein by binding to its cyclin partner. However, the cell cycle must be restricted when undergoing abnormal changes. Most cancers correlate to the deregulated cell cycle, and since Cdks are a central component of the cell cycle, Cdk inhibitors are extensively studied to develop anticancer agents. For instance, cyclin D associates with several Cdks, such as Cdk 4/6, to form an active complex. The cyclin D-Cdk4/6 complex...
M-Cdk Drives Transition Into Mitosis02:15

M-Cdk Drives Transition Into Mitosis

Checkpoints throughout the cell cycle serve as safeguards and gatekeepers, allowing the cell cycle to progress in favorable conditions and slow or halt it in problematic ones. This regulation is known as the cell cycle control system.
Cyclin-dependent kinases, or Cdks, work in concert with cyclins to control cell cycle transitions. M-Cdk, a complex of Cdk1 bound to M cyclin, is a well-known example of this coordinated control that drives the transition from the G2 to the M phase.
M cyclin...
M-Cdk Drives Transition Into Mitosis02:15

M-Cdk Drives Transition Into Mitosis

Checkpoints throughout the cell cycle serve as safeguards and gatekeepers, allowing the cell cycle to progress in favorable conditions and slow or halt it in problematic ones. This regulation is known as the cell cycle control system.
Cyclin-dependent kinases, or Cdks, work in concert with cyclins to control cell cycle transitions. M-Cdk, a complex of Cdk1 bound to M cyclin, is a well-known example of this coordinated control that drives the transition from the G2 to the M phase.
M cyclin...