Active Projects

Regulation and drug targeting of cyclin-dependent kinases

The cyclin-dependent kinases (CDKs) are the master regulators of the eukaryotic cell cycle. Activation of the CDKs is triggered by the binding of an activating cyclin subunit, which drives conformational changes in the kinase domain to bring about kinase activation. Work in our group has uncovered the molecular mechanisms of allosteric coupling between kinase and cyclin subunits, and revealed that CDK inhibitors have far stronger allosteric effects than previously recognized. Current efforts are focused on studying how evolutionary divergence among CDKs has altered the allosteric coupling between the cyclin and CDK subunits, resulting in altered activation dynamics and pronounced differences in inhibitor recognition. 

Overcoming paradoxical activation of BRAF

BRAF kinase is a central component of the MAPK signaling pathway that couples growth factor receptors to downstream effects on cell growth and proliferation. BRAF is mutated in a variety of human cancers, and ~50% of melanomas are driven by a single V600E mutation. Remarkably, inhibitors developed to block BRAF signaling can in certain circumstances instead activate the kinase. This "paradoxical activation" leads to secondary tumor development in patients treated with BRAF inhibitors, and is thought to be due to inhibitor-driven BRAF dimerization in which one protomer of the dimer remains free of inhibitor. We are studying the mechanisms underlying paradoxical activation by dissecting the thermodynamic, structural and dynamic effects that couple  inhibitor binding to BRAF dimerization.

Dissecting allosteric scaffolding interactions of Aurora kinases

The Aurora kinases are a family of serine/threonine protein kinases that play critical roles in mitosis. Aurora A regulates the formation of the mitotic spindle and Aurora B is important for spindle attachment and cytokinesis. Aurora A has a wealth of interaction partners, and these protein-protein interactions recruit the kinase to different cellular locations to perform a range of functions. For instance, Aurora A is recruited to nascent spindle microtubules and activated by the microtubule binding protein Tpx2, but is also activated by the protein Bora in a pathway that regulates mitotic entry, and forms a scaffolding complex with the oncogenic transcription factors N-Myc and c-Myc that protects them from proteolytic degradation. We are studying how the diverse array of allosteric interactions of Aurora A and Aurora B regulate kinase function and modulate inhibitor recognition. In fact, it turns out that these different allosteric regulators profoundly alter allosteric interactions with inhibitors.