Related Experiment Video
Updated: Aug 9, 2026

10:55
Study of the DNA Damage Checkpoint using Xenopus Egg Extracts
Published on: November 5, 2012
Ku affects the ATM-dependent S phase checkpoint following ionizing radiation
Xiang-Yang Zhou1, Xiang Wang, Hongyan Wang
1Department of Radiation Oncology, Kimmel Cancer Center of Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, PA 19107, USA.
Oncogene
|September 6, 2002
Summary
Genotoxic stress triggers cell cycle arrest for DNA repair. Ku80-deficient cells show a stronger S phase checkpoint response due to increased ATM kinase activity following irradiation.
Area of Science:
- Cellular Biology
- Molecular Biology
- Genetics
Background:
- Proliferating cells utilize S phase checkpoints to pause DNA replication after genotoxic stress, allowing time for DNA repair.
- The ATM-dependent pathway is crucial for the S phase checkpoint response to ionizing radiation.
Purpose of the Study:
- To investigate the role of Ku80 in the S phase checkpoint response to DNA damage.
- To elucidate the mechanisms underlying the enhanced S phase checkpoint in Ku80-deficient cells.
Main Methods:
- Comparison of S phase checkpoint response in irradiated Ku80(-/-) cells and wild-type counterparts.
- Assessment of ATM and DNA-dependent protein kinase (DNA-PK) activity.
- Inhibition of ATM using wortmannin and ATM antisense oligonucleotide.
Main Results:
- Ku80(-/-) cells exhibited a stronger S phase checkpoint response compared to wild-type cells after irradiation.
- This enhanced response correlated with higher ATM activity and increased ATM binding to chromatin DNA.
- Wortmannin and ATM antisense oligonucleotide treatments abolished the stronger S phase checkpoint in Ku80(-/-) cells.
Conclusions:
- The enhanced S phase checkpoint in irradiated Ku80(-/-) cells is attributed to elevated ATM kinase activity.
- ATM kinase activity, rather than DNA-PK activity, is the key factor driving the stronger checkpoint response in these cells.
Keywords:
Non-programmaticMore Related Videos
Related Concept Videos
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 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 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...
Mutations
Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. Mutations can be characterized in a number of different ways: whether and how they alter the amino acid sequence of the protein, whether they occur over a small or large area of DNA, and whether they occur in somatic cells or germline cells.
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...
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 Cell Cycle Control System
The cell cycle regulation directs how a cell proceeds from one phase to the next and begins mitosis. The cell cycle control system includes intracellular regulatory molecules and external triggers. They provide "stop" or "advance" signals and operate at specific cell cycle stages termed checkpoints to ensure that a particular process is completed before the cell advances to the next phase.
Cyclins and cyclin-dependent kinases (Cdks) are the primary cell cycle regulators and function at the cell...
Cyclins and cyclin-dependent kinases (Cdks) are the primary cell cycle regulators and function at the cell...

