Related Experiment Video

Updated: Aug 7, 2026

Analysis of Cell Cycle Position in Mammalian Cells
12:19

Analysis of Cell Cycle Position in Mammalian Cells

Published on: January 21, 2012

Differential effects of cdk2 and cdk3 on the control of pRb and E2F function during G1 exit

F Hofmann1, D M Livingston

  • 1Division of Neoplastic Disease Mechanisms, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.

Genes & Development
|April 1, 1996
PubMed

Insights

Cyclin-dependent kinases (CDKs) 2 and 3 are crucial for cell cycle progression. SV40 T antigen cannot overcome G1 arrest caused by dominant-negative CDK3, highlighting CDK3

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Cyclin-dependent kinases (CDKs) 2 and 3 regulate the G1-S phase transition in mammalian cells.
  • SV40 T antigen (T) is known to interfere with cell cycle regulation.
  • pRb and related pocket proteins negatively regulate E2F transcription factors.

Purpose of the Study:

  • To investigate the roles of CDK2 and CDK3 in mammalian cell cycle progression.
  • To determine how SV40 T antigen interacts with CDK2 and CDK3 pathways.
  • To elucidate the specific functions of CDK3 in E2F transcription factor regulation.

Main Methods:

  • Utilized dominant-negative mutants of CDK2 (cdk2dn) and CDK3 (cdk3dn) to induce G1 arrest.
  • Assessed the effect of SV40 T antigen on cell cycle progression and E2F activity in the presence of these mutants.
  • Performed co-immunoprecipitation to study in vivo interactions between CDK3 and E2F/DP-1 complexes.

Main Results:

  • G1 arrest induced by cdk2dn or cdk3dn was resistant to SV40 T antigen.
  • In cdk2dn cells, T antigen released E2F but failed to induce S-phase, indicating CDK2 phosphorylates non-pocket protein substrates.
  • In cdk3dn cells, T antigen could not induce cell cycle progression or E2F-dependent transcription, as dominant-negative CDK3 inhibited E2F-1, E2F-2, and partially E2F-3 activity independently of pRb.

Conclusions:

  • CDK2 phosphorylates non-pocket protein substrates essential for S-phase entry, a function not fully mimicked by SV40 T antigen.
  • CDK3 is critical for activating E2F-1, E2F-2, and partially E2F-3, playing a key role in S-phase entry through a pRb-independent mechanism.
  • CDK3 directly interacts with E2F-1/DP-1 complexes, likely mediating its regulatory function on these transcription factors.

More Related Videos

Studying Cell Cycle-regulated Gene Expression by Two Complementary Cell Synchronization Protocols12:02

Studying Cell Cycle-regulated Gene Expression by Two Complementary Cell Synchronization Protocols

Published on: June 6, 2017

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay12:26

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

Published on: May 3, 2018

Related Concept Videos

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.
Negative Regulator Molecules01:23

Negative Regulator Molecules

Positive regulators allow a cell to advance through cell cycle checkpoints. Negative regulators have an equally important role as they terminate a cell’s progression through the cell cycle—or pause it—until the cell meets specific criteria.
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.
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...
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...