A Covalently Bound Inhibitor Triggers EZH2 Degradation Through CHIP-mediated Ubiquitination

Wang X, et al., 36(9):1243-1260, EMBO J, 2017

EZH2 is a histone methyltransferase that plays a role in regulating chromatin structure during gene expression in normal tissue. Elevated and aberrant EZH2 expression has also been found in malignant tumors, therefore making it a promising drug target. This study identified gambogenic acid (GNA) and a derivative, GNA002, as chemical inhibitors that specifically and covalently bind EZH2 in its methyltransferase domain resulting in protein degradation through CHIP-mediated ubiqitination. Several binding analyses were performed including a competition assay using a Pall Fortebio Octet. Binding curves were generated by capturing biotinylated-GNA on SSA biosensors and titrated against the EZH2 methyltransferase domain in the presence of GNA or GNA002. The results demonstrate that both GNA and GNA002 compete with biotinylated-GNA to bind EZH2 in its methyltransferase domain with GNA002 having a stronger inhibition effect than GNA. The Octet platform allowed for all binding assays to be performed in parallel and carried out with controls for non-specific binding and signal drift over time.

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