John H. Bushweller, PhD
Structural biology of leukemia related proteins; targeted drug design for leukemia
The Bushweller lab is fundamentally interested in understanding, from a structural and biophysical perspective, the functioning of proteins involved in regulating transcription, particularly those involved in the dysregulation associated with the development of leukemia. Structural and functional characterization of the native forms of these proteins and their relevant complexes via NMR spectroscopy or x-ray crystallography and a variety of other techniques provides a baseline of understanding. Subsequent characterization of the oncoprotein forms then provides a detailed understanding of the molecular mechanism of oncogenesis associated with altered forms of these proteins. Such knowledge leads to novel avenues for the design of therapeutic agents to treat the cancers associated with these particular oncoproteins.
Their current focus is structural studies of core-binding factor (CBF). This heterodimeric complex (CBF? and CBF?) is essential for hematopoietic development. Gene translocations associated with the genes coding for the two subunits of CBF produce novel fusion proteins which have been implicated as playing a role in more than 30% of acute leukemias. They have completed structural studies of the two proteins of the heterodimeric CBF as well as of the relevant complexes with each other and with DNA. They are now conducting structural and functional studies of oncoprotein forms of the two subunits of CBF that are associated with leukemia. They have shown that the inv(16) translocation, involving the CBF? subunit, results in a protein with altered affinity for the CBF? subunit. This helps explain the dominant negative phenotype of this protein and the origins of its leukemogenesis. They have recently solved the structure of the oligomerization domain of the t(8;21) protein, AML1-ETO, which fuses CBF? with the co-repressor ETO. Using the structure they have designed point mutations to convert the protein to a monomeric form and shown that this abrogates the ability of AML1-ETO to mediate proliferation of bone marrow cells. They are using NMR to study the structure and function of the AML1-ETO domain responsible for SMRT and N-CoR recruitment. This work is now funded by an R01 from NCI. The x-ray crystallography is a collaborative project with Dr. Wladek Minor, also in Program 5.