Related Experiment Video

Updated: Aug 19, 2026

Analysis of Cell Cycle Position in Mammalian Cells
12:19

Analysis of Cell Cycle Position in Mammalian Cells

Published on: January 21, 2012

PP2A-dependent transactivation of the cyclin A promoter by SV40 ST is mediated by a cell cycle-regulated E2F site

Christine Skoczylas1, Berthold Henglein, Kathleen Rundell

  • 1Department of Microbiology-Immunology, Northwestern University, 303 E. Chicago Avenue, Chicago, IL 60611, USA.

Virology
|February 1, 2005
PubMed

Insights

Simian Virus 40 (SV40) small-t antigen (ST) drives cell proliferation and enhances transformation. ST interacts with protein phosphatase 2A (PP2A) to activate the cyclin A promoter.

Area of Science:

  • Virology
  • Molecular Biology
  • Cell Biology

Background:

  • Simian Virus 40 (SV40) is a DNA tumor virus.
  • The SV40 small-t antigen (ST) is implicated in viral oncogenesis and cell cycle regulation.
  • Understanding ST's molecular mechanisms is crucial for cancer research.

Purpose of the Study:

  • To elucidate the molecular mechanisms by which SV40 ST regulates cell proliferation.
  • To identify the specific cellular targets and pathways modulated by ST.
  • To investigate the role of protein phosphatase 2A (PP2A) in ST-mediated transactivation.

Main Methods:

  • Analysis of SV40 ST interactions with cellular proteins.
  • Reporter gene assays to measure promoter activity (e.g., cyclin A promoter).
  • Cell cycle analysis and proliferation assays.

Main Results:

  • SV40 ST enhances cell proliferation and transformation, partly by targeting p27 and cyclin A.
  • ST-mediated transactivation of the cyclin A promoter requires interaction with PP2A.
  • This activation occurs via a cell cycle-regulated E2F site on the cyclin A promoter.

Conclusions:

  • SV40 ST utilizes PP2A to modulate the cyclin A promoter, contributing to cell cycle dysregulation.
  • The findings provide insights into viral mechanisms of cell proliferation and transformation.
  • ST's interaction with PP2A represents a key step in SV40-induced oncogenesis.

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 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...
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.
Mitogens and the Cell Cycle02:38

Mitogens and the Cell Cycle

Mitogens and their receptors play a crucial role in controlling the progression of the cell cycle. However, the loss of mitogenic control over cell division leads to tumor formation. Therefore, mitogens and mitogen receptors play an important role in cancer research. For instance, the epidermal growth factor (EGF) - a type of mitogen and its transmembrane receptor (EGFR), decides the fate of the cell's proliferation. When EGF binds to EGFR, a member of the ErbB family of tyrosine kinase...
Anaphase Promoting Complex00:50

Anaphase Promoting Complex

The stepwise destruction of specific proteins is necessary for the progression and completion of the cell cycle. Such proteins are ubiquitinated by ubiquitin ligases and then subsequently destroyed by the proteasome. The SCF (Skp1/Cullin/F-box) and the anaphase-promoting complex (APC) are two important ubiquitin ligases involved in cell cycle progression. While SCF is active throughout the cell cycle, APC gets activated during metaphase to anaphase transition. Cdc20 or Cdh1 binds to APC and...