The cell cycle checkpoint kinase CHK2 mediates DNA damage-induced stabilization of TTK/hMps1.
Cell cycle progression is monitored constantly to ensure faithful passage of genetic codes and genome stability. We have demonstrated previously that, upon DNA damage, TTK/hMps1 activates the checkpoint kinase CHK2 by phosphorylating CHK2 at Thr68. However, it remains to be determined whether and how TTK/hMps1 responds to DNA damage. In this report, we present evidence that TTK/hMps1 can be induced by DNA damage in normal human fibroblasts. Interestingly, the induction depends on CHK2 because CHK2-targeting small interfering RNA or a CHK2 inhibitor abolishes the increase. Such induction is mediated through phosphorylation of TTK/hMps1 at Thr288 by CHK2 and requires the CHK2 SQ/TQ cluster domain/forkhead-associated domain. In cells, TTK/hMps1 phosphorylation at Thr288 is induced by DNA damage and forms nuclear foci, which colocalize partially with gamma-H2AX. Reexpression of TTK/hMps1 T288A mutant in TTK/hMps1-knockdown cells causes a defect in G(2)/M arrest, suggesting that phosphorylation at this site participates in the proper checkpoint execution. Our study uncovered a regulatory loop between TTK/hMps1 and CHK2 whereby DNA damage-activated CHK2 may facilitate the stabilization of TTK/hMps1, therefore maintaining the checkpoint control.
Yeh
Y-H
YH
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
Huang
Y-F
YF
Lin
T-Y
TY
Shieh
S-Y
SY
D018797:Cell Cycle Proteins / Q000378:metabolism*; D002455:Cell Division; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D016195:G2 Phase; D006367:HeLa Cells; D006801:Humans; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D011505:Protein-Tyrosine Kinases
D018797:Cell Cycle Proteins; D064447:Checkpoint Kinase 2; D011505:Protein-Tyrosine Kinases; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases; C075840:TTK protein, human