Related Experiment Video

Updated: Aug 30, 2026

Manipulation and Analysis of Cell Cycle-Dependent Processes in Budding Yeast
08:13

Manipulation and Analysis of Cell Cycle-Dependent Processes in Budding Yeast

Published on: September 26, 2025

DNA damage during the spindle-assembly checkpoint degrades CDC25A, inhibits cyclin-CDC2 complexes, and reverses cells

Jeremy P H Chow1, Wai Yi Siu, Tsz Kan Fung

  • 1Department of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong.

Molecular Biology of the Cell
|October 1, 2003
PubMed

Insights

Cells experiencing DNA damage during mitotic arrest do not die but enter a G2-like state. This response, dependent on ATM, prevents cell cycle progression into G1, even after the mitotic block is removed.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • Cell cycle checkpoints are crucial for maintaining genetic integrity.
  • Targeting cell cycle checkpoints is a key strategy in cancer chemotherapy.
  • Understanding cellular responses to simultaneous DNA damage and spindle disruption is vital.

Purpose of the Study:

  • To investigate cellular responses to DNA damage when the spindle-assembly checkpoint is active.
  • To elucidate the molecular mechanisms governing cell cycle progression under conflicting checkpoint signals.

Main Methods:

  • Single cell electrophoresis to detect DNA damage.
  • Histone H2AX and H3 phosphorylation analysis.
  • Western blotting for cell cycle regulators (e.g., CDC2, cyclins, CDC25A).
  • Caspase-3 activation and DNA fragmentation assays to assess cell death.

Main Results:

  • Chemotherapeutic agents induced DNA damage during mitotic block, leading to CDC2 inactivation and chromosome decondensation.
  • Cells with DNA damage during mitosis entered a G2-like state (4N DNA) without progressing to G1.
  • This response was ATM-dependent, independent of p53 and pRb, and did not involve apoptosis.
  • ATM-mediated degradation of CDC25A was critical for preventing G1 entry.

Conclusions:

  • Conflicting signals from DNA damage and spindle checkpoints are resolved by the DNA damage checkpoint's dominance.
  • ATM-dependent pathways mediate a robust G2-like arrest in response to DNA damage during mitosis.
  • This mechanism prevents the propagation of damaged DNA and highlights potential therapeutic vulnerabilities.

More Related Videos

Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations10:54

Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations

Published on: September 17, 2012

Detection of DNA Double-Stranded Breaks in Mouse Oocytes07:46

Detection of DNA Double-Stranded Breaks in Mouse Oocytes

Published on: June 23, 2023

Related Concept Videos

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...
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...
The Spindle Assembly Checkpoint02:19

The Spindle Assembly Checkpoint

The spindle assembly checkpoint is a molecular surveillance mechanism ensuring the fidelity of chromosome segregation during anaphase. The checkpoint monitors the completion of all the prerequisite steps before chromosome segregation to determine whether the segregation process should proceed or be delayed.
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
The Spindle Assembly Checkpoint02:19

The Spindle Assembly Checkpoint

The spindle assembly checkpoint is a molecular surveillance mechanism ensuring the fidelity of chromosome segregation during anaphase. The checkpoint monitors the completion of all the prerequisite steps before chromosome segregation to determine whether the segregation process should proceed or be delayed.
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
Separation of Sister Chromatids02:17

Separation of Sister Chromatids

At the transition from prophase to metaphase, there is a reduction in cohesion along the chromosomal arms, resulting in the resolution of sister chromatids. However, residual cohesin connections remain to hold the sister chromatids together until the transition from metaphase to anaphase. The residual connection prevents any premature separation of sister chromatids, blocking the risks of aneuploidy within the daughter cells.
At the onset of anaphase, separase, a proteolytic enzyme, is...
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...