title: Threonine 68 of Chk2 is phosphorylated at sites of DNA strand breaks.
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.
authors.affiliation: Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: I M
authors.initials: IM
authors.lastname: Ward
authors.forename: X
authors.initials: X
authors.lastname: Wu
authors.forename: J
authors.initials: J
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000201:enzymology / Q000528:radiation effects; D064447:Checkpoint Kinase 2; D004247:DNA / Q000737:chemistry / Q000528:radiation effects*; D004249:DNA Damage; D004789:Enzyme Activation; D005720:Gamma Rays; D007700:Kinetics; D010766:Phosphorylation; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D013912:Threonine / Q000378:metabolism*
chemical_list: D013912:Threonine; D004247:DNA; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; D017346:Protein Serine-Threonine Kinases