Phosphorylation of threonine 68 promotes oligomerization and autophosphorylation of the Chk2 protein kinase via the forkhead-associated domain.

Phosphorylation of Thr-68 by the ataxia telangiectasia-mutated is necessary for efficient activation of Chk2 when cells are exposed to ionizing radiation. By an unknown mechanism, this initial event promotes additional autophosphorylation events including modifications of Thr-383 and Thr-387, two amino acid residues located within the activation loop segment within the ...
Chk2 catalytic domain. Chk2 and related kinases possess one or more Forkhead-associated (FHA) domains that are phosphopeptide-binding modules believed to be crucial for their checkpoint control activities. We show that the Chk2 FHA domain is dispensable for Thr-68 phosphorylation but necessary for efficient autophosphorylation in response to ionizing radiation. Phosphorylation of Thr-68 promotes oligomerization of Chk2 by serving as a specific ligand for the FHA domain of another Chk2 molecule. In addition, Chk2 phosphorylates its own FHA domain, and this modification reduces its affinity for Thr-68-phosphorylated Chk2. Thus, activation of Chk2 in irradiated cells may occur through oligomerization of Chk2 via binding of the Thr-68-phosphorylated region of one Chk2 to the FHA domain of another. Oligomerization of Chk2 may therefore increase the efficiency of trans-autophosphorylation resulting in the release of active Chk2 monomers that proceed to enforce checkpoint control in irradiated cells.
Mesh Terms:
Amino Acid Sequence, Forkhead Transcription Factors, Glutathione Transferase, Humans, Ligands, Molecular Sequence Data, Mutation, Nuclear Proteins, Peptides, Phosphorylation, Precipitin Tests, Protein Binding, Protein Kinases, Protein Structure, Tertiary, Protein-Serine-Threonine Kinases, Recombinant Proteins, Threonine, Transcription Factors
J. Biol. Chem.
Date: May. 31, 2002
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