Related Experiment Video

Updated: Sep 21, 2026

Analysis of Cell Cycle Position in Mammalian Cells
12:19

Analysis of Cell Cycle Position in Mammalian Cells

Published on: January 21, 2012

E2F1-induced apoptosis requires DNA binding but not transactivation and is inhibited by the retinoblastoma protein

J K Hsieh1, S Fredersdorf, T Kouzarides

  • 1Ludwig Institute for Cancer Research, Imperial College School of Medicine at St. Mary's, London, UK.

Genes & Development
|July 15, 1997
PubMed

Insights

E2F1 can induce apoptosis without p53 or Rb. Retinoblastoma protein (Rb) inhibits this E2F1-induced apoptosis, suggesting a novel role for Rb in controlling cell death pathways.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • E2F1 is known to induce apoptosis, often in conjunction with p53.
  • The role of E2F1 in apoptosis independent of p53 and retinoblastoma protein (Rb) is less understood.
  • Rb is a key regulator of the cell cycle and can influence apoptosis.

Purpose of the Study:

  • To investigate whether E2F1 can induce apoptosis independently of p53 and Rb.
  • To elucidate the mechanism by which Rb inhibits E2F1-induced apoptosis.
  • To explore the relationship between E2F1's transactivation, DNA-binding activity, and its apoptotic function.

Main Methods:

  • Overexpression of wild-type and mutant forms of E2F1 in Saos-2 cells (p53 and Rb null).
  • Assessment of apoptosis induction by E2F1 and its mutants.
  • Analysis of the inhibitory effect of Rb and mdm2 on E2F1-induced apoptosis.
  • Mutation analysis to uncouple transactivation, DNA-binding, and apoptotic functions of E2F1.

Main Results:

  • E2F1 overexpression induces apoptosis in Saos-2 cells lacking p53 and functional Rb.
  • Rb specifically inhibits E2F1-induced apoptosis, while mdm2 does not.
  • The transactivation and apoptotic functions of E2F1 are uncoupled; DNA-binding is essential for apoptosis.
  • Rb inhibits apoptosis induced by wild-type E2F1 and Rb-binding-competent mutants, but not by Rb-binding-defective mutants.

Conclusions:

  • E2F1 possesses a p53- and Rb-independent apoptotic function.
  • Rb inhibits E2F1-induced apoptosis through mechanisms distinct from transactivation suppression.
  • Transcriptional repression, rather than transactivation, may mediate E2F1's apoptotic function, highlighting a novel role for the Rb-E2F1 complex in controlling apoptosis.

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

Mapping the Structure-Function Relationships of Disordered Oncogenic Transcription Factors Using Transcriptomic Analysis09:58

Mapping the Structure-Function Relationships of Disordered Oncogenic Transcription Factors Using Transcriptomic Analysis

Published on: June 27, 2020

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.
Eukaryotic Transcription Inhibitors01:52

Eukaryotic Transcription Inhibitors

Certain biochemical processes, such as embryonic development and cell growth regulation, depend on the repression of specific genes. DNA binding proteins known as eukaryotic transcription inhibitors regulate the repression of gene expression in eukaryotes. The presence of these inhibitors at the required location and time in the cell is triggered by the presence of hormones and additional signals from other cells.
Eukaryotic transcription inhibitors usually contain two distinct domains, a DNA...
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,...
The Extrinsic Apoptotic Pathway01:17

The Extrinsic Apoptotic Pathway

The extrinsic apoptotic pathway is initiated when extracellular death-inducing signals, such as specific cytokines, activate the death receptors expressed on the cell surface. The immune cells involved in this pathway are natural killer cells (NK cells) and cytotoxic T-lymphocytes. NK cells are critical in innate immune response, while cytotoxic T-lymphocytes are associated with adaptive immune response. These cells recognize specific receptors expressed on the altered cells and activate...
The Intrinsic Apoptotic Pathway01:31

The Intrinsic Apoptotic Pathway

Internal cellular stress, such as cellular injury or hypoxia, triggers intrinsic apoptosis. The B-cell lymphoma 2 (Bcl-2) family of proteins are the primary regulators of the intrinsic apoptotic pathway. For example, during DNA damage, checkpoint proteins, such as Ataxia Telangiectasia Mutated (ATM protein) and Checkpoints Factor-2 (Chk2) proteins, are activated. These proteins phosphorylate p53 which further activates pro-apoptotic proteins, such as Bax, Bak, PUMA, and Noxa, and inhibits...