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Updated: Aug 15, 2026

Two- and Three-Dimensional Live Cell Imaging of DNA Damage Response Proteins
Published on: September 28, 2012
Threonine 68 of Chk2 is phosphorylated at sites of DNA strand breaks
1Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA.
Abstract:
The protein kinase Chk2 has been implicated in signaling DNA damage to cell cycle checkpoints. In response to ionizing radiation, Chk2 becomes rapidly phosphorylated at threonine 68 by ataxia-telangiectasia mutated (ATM). Here we show that the Thr(68)-phosphorylated form of Chk2 forms distinct nuclear foci in response to ionizing radiation. Only this activated form of Chk2 localizes at sites of DNA strand breaks. The kinase activity of Chk2 and the number of Chk2 foci formed depend on the severity of DNA damage and gradually decline correlating with the predicted value of slowly re-joining double strand breaks. These results suggest that Chk2 is regulated at the sites of DNA strand breaks in response to ionizing radiation.
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