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10:55
Study of the DNA Damage Checkpoint using Xenopus Egg Extracts
Published on: November 5, 2012
ATR dependent activation of Chk2
Xiao Qi Wang1, J Leslie Redpath, Sheung Tat Fan
1Department of Radiation Oncology, University of California Irvine, California, USA.
Journal of Cellular Physiology
|June 3, 2006
Summary
The study reveals that ATR phosphorylates Chk2, a key DNA damage response protein. This occurs even when ATM is deficient, highlighting ATR
Area of Science:
- Cellular Biology
- Molecular Biology
- Genetics
Background:
- ATM and ATR are crucial kinases regulating DNA damage checkpoints in mammalian cells.
- ATM primarily acts through Chk2, while ATR acts through Chk1.
- Limited cross-regulation exists between ATM-Chk2 and ATR-Chk1 pathways, despite overlapping functions.
Purpose of the Study:
- To investigate the role of ATR in phosphorylating Chk2.
- To explore the interplay between ATM and ATR in response to DNA damage.
- To determine if ATR can phosphorylate Chk2 in ATM-deficient cells.
Main Methods:
- Utilized ionizing radiation (IR) and ultraviolet (UV) radiation to induce DNA damage.
- Employed caffeine to inhibit ATM activity.
- Assessed ATR activation and Chk2 phosphorylation (total and Thr68) in various cell lines, including ATM-deficient and ATM-silenced cells.
- Performed in vitro kinase assays.
Main Results:
- ATR phosphorylates Chk2 in response to both IR and UV radiation.
- ATR activation by IR is enhanced in the presence of caffeine (ATM inhibition), leading to Chk2 hyperphosphorylation.
- ATR activation by UV radiation is normal in ATM-+/+ and ATM-/- cells and is caffeine-sensitive.
- In ATM-deficient cells, ATR is activated by IR and phosphorylates Chk2 in vitro.
Conclusions:
- ATR acts as a kinase for Chk2, particularly under conditions of DNA damage.
- ATR-mediated Chk2 phosphorylation is evident even when ATM is deficient or inhibited.
- These findings suggest ATR's significant role in Chk2 phosphorylation during the DNA damage response, especially in ATM-compromised scenarios.
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