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Structural basis for Chk1 inhibition by UCN-01
Baoguang Zhao1, Michael J Bower, Patrick J McDevitt
1Department of Structural Biology, GlaxoSmithKline, King of Prussia, Pennsylvania 19406, USA.
Abstract:
Chk1 is a serine-threonine kinase that plays an important role in the DNA damage response, including G(2)/M cell cycle control. UCN-01 (7-hydroxystaurosporine), currently in clinical trials, has recently been shown to be a potent Chk1 inhibitor that abrogates the G(2)/M checkpoint induced by DNA-damaging agents. To understand the structural basis of Chk1 inhibition by UCN-01, we determined the crystal structure of the Chk1 kinase domain in complex with UCN-01. Chk1 structures with staurosporine and its analog SB-218078 were also determined. All three compounds bind in the ATP-binding pocket of Chk1, producing only slight changes in the protein conformation. Selectivity of UCN-01 toward Chk1 over cyclin-dependent kinases can be explained by the presence of a hydroxyl group in the lactam moiety interacting with the ATP-binding pocket. Hydrophobic interactions and hydrogen-bonding interactions were observed in the structures between UCN-01 and the Chk1 kinase domain. The high structural complementarity of these interactions is consistent with the potency and selectivity of UCN-01.
Insights
The crystal structure reveals how UCN-01, a Chk1 inhibitor, binds to the Chk1 kinase domain. This provides insight into the DNA damage response and cell cycle control mechanisms.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Checkpoint kinase 1 (Chk1) is crucial for the DNA damage response and G(2)/M cell cycle control.
- UCN-01 (7-hydroxystaurosporine) is a potent Chk1 inhibitor currently in clinical trials, known to abrogate DNA damage-induced G(2)/M checkpoints.
Purpose of the Study:
- To elucidate the structural basis of Chk1 inhibition by UCN-01.
- To understand the molecular interactions responsible for UCN-01's potency and selectivity.
Main Methods:
- X-ray crystallography was employed to determine the crystal structure of the Chk1 kinase domain.
- Structures were solved for Chk1 in complex with UCN-01, staurosporine, and SB-218078.
Main Results:
- All three inhibitors (UCN-01, staurosporine, SB-218078) bind within the ATP-binding pocket of Chk1 with minimal conformational changes.
- The selectivity of UCN-01 for Chk1 over cyclin-dependent kinases is attributed to a hydroxyl group in its lactam moiety interacting with the ATP-binding pocket.
- Detailed hydrophobic and hydrogen-bonding interactions between UCN-01 and the Chk1 kinase domain were identified.
Conclusions:
- The determined crystal structures provide a detailed molecular understanding of Chk1 inhibition by UCN-01.
- The structural insights support the observed potency and selectivity of UCN-01 as a Chk1 inhibitor.
- This structural information can aid in the design of novel Chk1-targeting therapeutics for cancer treatment.