Inhibition of Chk1 by the G[subscript 2] DNA damage checkpoint inhibitor isogranulatimide
Journal Article
·
· Mol. Cancer Ther.
OSTI ID:1008761
- Kinetek
Inhibitors of the G{sub 2} DNA damage checkpoint can selectively sensitize cancer cells with mutated p53 to killing by DNA-damaging agents. Isogranulatimide is a G{sub 2} checkpoint inhibitor containing a unique indole/maleimide/imidazole skeleton identified in a phenotypic cell-based screen; however, the mechanism of action of isogranulatimide is unknown. Using natural and synthetic isogranulatimide analogues, we show that the imide nitrogen and a basic nitrogen at position 14 or 15 in the imidazole ring are important for checkpoint inhibition. Isogranulatimide shows structural resemblance to the aglycon of UCN-01, a potent bisindolemaleimide inhibitor of protein kinase C{beta} (IC{sub 50}, 0.001 micromol/L) and of the checkpoint kinase Chk1 (IC{sub 50}, 0.007 micromol/L). In vitro kinase assays show that isogranulatimide inhibits Chk1 (IC{sub 50}, 0.1 {micro}mol/L) but not protein kinase C{beta}. Of 13 additional protein kinases tested, isogranulatimide significantly inhibits only glycogen synthase kinase-3{beta} (IC{sub 50}, 0.5 {micro}mol/L). We determined the crystal structure of the Chk1 catalytic domain complexed with isogranulatimide. Like UCN-01, isogranulatimide binds in the ATP-binding pocket of Chk1 and hydrogen bonds with the backbone carbonyl oxygen of Glu{sup 85} and the amide nitrogen of Cys{sup 87}. Unlike UCN-01, the basic N15 of isogranulatimide interacts with Glu{sub 17}, causing a conformation change in the kinase glycine-rich loop that may contribute importantly to inhibition. The mechanism by which isogranulatimide inhibits Chk1 and its favorable kinase selectivity profile make it a promising candidate for modulating checkpoint responses in tumors for therapeutic benefit.
- Research Organization:
- Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1008761
- Journal Information:
- Mol. Cancer Ther., Journal Name: Mol. Cancer Ther. Journal Issue: 10, 2004 Vol. 3
- Country of Publication:
- United States
- Language:
- ENGLISH
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