Inhibitor Selectivity for Cyclin-Dependent Kinase 7: A Structural, Thermodynamic, and Modelling Study

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Discovery

Background:

• Cell cycle deregulation, particularly elevated cyclin-dependent kinase (CDK) activity, is a hallmark of human diseases, especially cancer.
• CDK7 plays a critical role by phosphorylating cell-cycle CDKs, thereby promoting their activity.

Purpose of the Study:

• To identify and characterize small-molecule inhibitors that selectively target CDK7.
• To elucidate the molecular mechanisms underlying the selectivity of these inhibitors for CDK7 over other CDKs.

Main Methods:

• X-ray crystallography to determine the structures of inhibitors bound to CDK2.
• Molecular dynamics (MD) simulations to model inhibitor binding to CDK2 and CDK7.
• Isothermal titration calorimetry (ITC) to experimentally validate binding interactions with wild-type and mutant CDK7 and CDK2.

Main Results:

• Crystal structures revealed inhibitor binding modes to CDK2, facilitating modeling of CDK7 interactions.
• MD simulations provided insights into inhibitor binding and the role of protein flexibility.
• ITC data identified specific residues, such as Asp155 in CDK7, critical for inhibitor selectivity.
• Flexibility in CDK7's G-rich and activation loops was identified as a key factor in inhibitor specificity, mirroring observations in CDK2.

Conclusions:

• Small-molecule inhibitors targeting CDK7 have been identified with potential for selective inhibition.
• Structural, biophysical, and computational methods elucidated key molecular determinants of CDK7 inhibitor selectivity.
• Understanding these interactions, including the role of specific residues and loop flexibility, is crucial for developing targeted cancer therapies.