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Area of Expertise: Regulation of the cell cycle by ubiquitin-dependent proteolysis; protein mass spectrometry

Regulation of cell division. During cell division, an organism’s genome must be accurately duplicated and then faithfully distributed to the two resulting daughter cells. Cancer can result from defects in cell division that compromise genome integrity. My lab is interested in the molecular regulatory mechanisms that ensure proper cell division. We currently focus on the roles that regulated proteolysis and protein phosphorylation play in coordinating the late stages of cell division, including chromosome segregation, mitotic exit, and cytokinesis. Proper coordination of these late events is important for maintaining genome stability. Current projects in the lab are centered on the following proteins:

The anaphase-promoting complex (APC)

The APC is a large, highly conserved, ubiquitin ligase complex that targets several important cell cycle regulatory proteins for proteasomal degradation at specific times during cell division. The APC is best known for its role in promoting chromosome segregation and mitotic exit by targeting securin and mitotic cyclins for destruction. However, the stability of numerous other proteins is controlled by the APC as well. We are studying how APC activity is regulated and how the APC specifically recognizes its substrates. Binding of pseudosubstrate inhibitors, such as the budding yeast Acm1 protein that we discovered several years ago, is a common mechanism for controlling APC activity. Pseudosubstrates are also useful tools for exploring the determinants for substrate recognition. Our work characterizing Acm1 will therefore improve our understanding of both APC regulation and substrate recognition.

Cdc14 phosphatase 

Cyclin-dependent kinase (Cdk) activity drives most of the major cell cycle events. However, inactivation of Cdk and reversal of Cdk phosphorylation sites are universal requirements for completing mitosis and triggering cytokinesis. The Cdc14 phosphatases have been implicated in reversal of Cdk phosphorylation and in budding yeast Cdc14 is essential for completion of mitosis. In collaboration with the Charbonneau lab in our department we are exploring substrate specificity of the Cdc14 phosphatase family. We are using our insights into Cdc14’senzymatic specificity to predict and then test novel substrates and biological functions.

14-3-3 proteins

The highly conserved 14-3-3 proteins are a family of abundant phosphoprotein chaperones that have been implicated in cancer and other diseases. Work from our lab and others has recently suggested that 14-3-3 proteins can specifically bind to Cdk-catalyzed phosphorylation sites. Beginning with targeted proteomic approaches we are undertaking studies to explore the hypothesis that effects of Cdk are commonly mediated by binding of 14-3-3 proteins to Cdk substrates.

Our research tools. The majority of our work is conducted in the budding yeast Saccharomyces cerevisiae. Budding yeast are easy to work with and manipulate genetically, making them an attractive model organism for studying conserved and fundamental biological processes, such as cell division. We apply biochemistry, cell biology, molecular biology, and genetics methods to our research projects, providing a diverse training experience for students. In addition, we use mass spectrometry in a variety of ways, particularly for the discovery, quantification, and characterization of protein-protein interactions and protein post-translational modifications.