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Checkpoint Kinase 2 (Chk2) Monomers or Dimers Phosphorylate Cdc25C After DNA Damage Regardless of Threonine 68 Phosphorylation

Checkpoint Kinase 2 (Chk2) Monomers or Dimers Phosphorylate Cdc25C After DNA Damage Regardless of Threonine 68 Phosphorylation

Jinwoo Ahn, Carol Prives

J Biol Chem. 2002 Dec 13;277(50):48418-26.

PMID: 12386164

Abstract:

We have purified and characterized human Chk2 both from baculovirus-infected insect cells and from either untreated or DNA damage-stressed human HCT116 cells. Chk2 from unstressed human cells is largely monomeric and inactive in phosphorylating its substrate, Cdc25C. It is also unphosphorylated at Thr-68, a site that is the target of the ataxia telangiectasia-mutated protein kinase. After treatment of HCT116 cells with a radiomimetic compound neocarzinostatin, active Chk2 exists as stable Thr-68-phosphorylated dimers as well as interconvertable Thr-68-unphosphorylated monomers and dimers. Interestingly, Chk2 from insect cells behaves by all criteria tested like active Chk2 from neocarzinostatin-treated HCT116 cells. Based on Stokes radius and sedimentation coefficient values, Chk2 monomers and dimers have asymmetric rather than globular shapes. Both Thr-68-phosphorylated and Thr-68-unphosphorylated forms of active Chk2 are capable of phosphorylating Cdc25C. Thus, although phosphorylation of Thr-68 may be required for initial oligomerization and activation of Chk2, it is not needed for maintenance of dimerization or kinase activity.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
IAR42411969	CHK2 active human			Price

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