Phosphorylation of threonine 68 promotes oligomerization and autophosphorylation of the Chk2 protein kinase via the forkhead-associated domain.
Article Details
- CitationCopy to clipboard
Ahn JY, Li X, Davis HL, Canman CE
Phosphorylation of threonine 68 promotes oligomerization and autophosphorylation of the Chk2 protein kinase via the forkhead-associated domain.
J Biol Chem. 2002 May 31;277(22):19389-95. Epub 2002 Mar 18.
- PubMed ID
- 11901158 [ View in PubMed]
- Abstract
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.