Related Experiment Video

Updated: Aug 12, 2026

Analysis of Cell Cycle Position in Mammalian Cells
12:19

Analysis of Cell Cycle Position in Mammalian Cells

Published on: January 21, 2012

Retinoblastoma growth suppressor and a 300-kDa protein appear to regulate cellular DNA synthesis

J A Howe1, J S Mymryk, C Egan

  • 1Department of Biology, McMaster University, Hamilton, ON, Canada.

Proceedings of the National Academy of Sciences of the United States of America
|August 1, 1990
PubMed

Insights

Adenovirus E1A proteins regulate DNA synthesis by interacting with retinoblastoma protein (p105-Rb) or p300. Binding to either protein is sufficient for inducing DNA synthesis in quiescent cells, suggesting parallel regulatory pathways.

Area of Science:

  • Molecular Biology
  • Virology
  • Cell Cycle Regulation

Background:

  • Oncogenic transformation by adenovirus type 5 E1A gene products is linked to interactions with cellular proteins.
  • Key interacting proteins identified include the retinoblastoma tumor suppressor gene product (p105-Rb) and a 300-kDa protein (p300).

Purpose of the Study:

  • To investigate the distinct roles of p105-Rb and p300 interactions in E1A-mediated oncogenic transformation versus induction of cellular DNA synthesis.
  • To differentiate the binding requirements of E1A for transformation versus DNA synthesis induction.

Main Methods:

  • Utilized viral mutants of adenovirus type 5 E1A.
  • Assessed the ability of E1A mutants to bind to p105-Rb and p300.
  • Measured the induction of cellular DNA synthesis in quiescent cells by E1A mutants.

Main Results:

  • E1A-mediated induction of cellular DNA synthesis in quiescent cells requires binding to either p105-Rb or p300.
  • Mutant E1A products that bind to neither p105-Rb nor p300 are severely defective in inducing DNA synthesis.
  • This contrasts with transformation, implying distinct binding requirements for these two processes.

Conclusions:

  • The retinoblastoma protein (p105-Rb) and p300 provide parallel pathways for regulating DNA synthesis induction by E1A.
  • These findings elucidate the differential mechanisms of E1A in cellular DNA synthesis regulation and oncogenic transformation.

More Related Videos

Inducible and Reversible Dominant-negative (DN) Protein Inhibition08:35

Inducible and Reversible Dominant-negative (DN) Protein Inhibition

Published on: January 7, 2019

Reconstruct Human Retinoblastoma In Vitro06:52

Reconstruct Human Retinoblastoma In Vitro

Published on: October 11, 2022

Related Concept Videos

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.
DNA Damage can Stall the Cell Cycle02:36

DNA Damage can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...
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...
Abnormal Proliferation02:23

Abnormal Proliferation

Under normal conditions, most adult cells remain in a non-proliferative state unless stimulated by internal or external factors to replace lost cells. Abnormal cell proliferation is a condition in which the cell's growth exceeds and is uncoordinated with normal cells. In such situations, cell division persists in the same excessive manner even after cessation of the stimuli, leading to persistent tumors. The tumor arises from the damaged cells that replicate to pass the damage to the daughter...
The Retinoblastoma Gene01:20

The Retinoblastoma Gene

Tumor suppressor genes are normal genes that can slow down cell division, repair DNA mistakes, or program the cells for apoptosis in case of irreparable damage. Hence, they play an essential role in preventing the proliferation of damaged cells.
The first-ever tumor suppressor gene called Rb was identified in retinoblastoma - a rare eye tumor in children. In inherited forms of the disease, a child inherits one defective copy of the Rb gene, which predisposes them to retinoblastoma. However,...
DNA Damage Can Stall the Cell Cycle02:36

DNA Damage Can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...