Identification and Characterization of Selective MLL1 CXXC Domain Inhibitors

Background

The MLL1 protein is subject to fusions with parts of other proteins. These fusions cause MLL1 to be active at inappropriate points in blood cell development, leading to leukemias with poor prognoses. Notably, they are found in over 70% of infant leukemias. MLL1 fusions can bind DNA via their CXXC domains. The Bushweller lab has demonstrated these mutations inhibit DNA binding, preventing leukemia in mouse cells. This makes the CXXC domain an excellent target for MLL leukemia treatment.  

CXXC domain-DNA interaction inhibitors will be identified using a fragment-based approach. Screening a large number of compounds that resemble parts of existing drugs likely to have only weak activity yields hits that can be modified or linked together to create more potent inhibitors. A 12,000 compound library has already been screened against this target, yielding 36 hits.

Project Goal

I will use NMR spectroscopy to verify that they bind to the CXXC domain and not DNA indiscriminately. Binding causes changes in chemical shift that I will quantify to determine where on the protein each hit binds, providing information about how they may be modified. I will screen those that verifiably bind the CXXC domain against a panel of the 11 other CXXC domains. Those hits that preferentially inhibit MLL1 will be prioritized for development and analyzed by saturation transfer difference experiments, which have the ability to show what parts of the compound are in closest contact with the protein and are therefore poor spots for chemical modification.