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Van Aller G.S.,Cancer Epigenetics Discovery Performance Unit | Pappalardi M.B.,Cancer Epigenetics Discovery Performance Unit | Ott H.M.,Cancer Epigenetics Discovery Performance Unit | Diaz E.,Glaxosmithkline | And 9 more authors.
ACS Chemical Biology | Year: 2014

EZH2/PRC2 catalyzes transcriptionally repressive methylation at lysine 27 of histone H3 and has been associated with numerous cancer types. Point mutations in EZH2 at Tyr641 and Ala677 identified in non-Hodgkin lymphomas alter substrate specificity and result in increased trimethylation at histone H3K27. Interestingly, EZH2/PRC2 is activated by binding H3K27me3 marks on histones, and this activation is proposed as a mechanism for self-propagation of gene silencing. Recent work has identified GSK126 as a potent, selective, SAM-competitive inhibitor of EZH2 capable of globally decreasing H3K27 trimethylation in cells. Here we show that activation of PRC2 by an H3 peptide trimethylated at K27 is primarily an effect on the rate-limiting step (k cat) with no effect on substrate binding (Km). Additionally, GSK126 is shown to have a significantly longer residence time of inhibition on the activated form of EZH2/PRC2 as compared to unactivated EZH2/PRC2. Overall inhibition constant (Ki*) values for GSK126 were determined to be as low as 93 pM and appear to be driven by slow dissociation of inhibitor from the activated enzyme. The data suggest that activation of EZH2 allows the enzyme to adopt a conformation that possesses greater affinity for GSK126. The long residence time of GSK126 may be beneficial in vivo and may result in durable target inhibition after drug systemic clearance. © 2013 American Chemical Society. Source

Verma S.K.,Cancer Epigenetics Discovery Performance Unit | Tian X.,Cancer Epigenetics Discovery Performance Unit | Lafrance L.V.,Cancer Epigenetics Discovery Performance Unit | Duquenne C.,Cancer Epigenetics Discovery Performance Unit | And 23 more authors.
ACS Medicinal Chemistry Letters | Year: 2012

The histone H3-lysine 27 (H3K27) methyltransferase EZH2 plays a critical role in regulating gene expression, and its aberrant activity is linked to the onset and progression of cancer. As part of a drug discovery program targeting EZH2, we have identified highly potent, selective, SAM-competitive, and cell-Active EZH2 inhibitors, including GSK926 (3) and GSK343 (6). These compounds are small molecule chemical tools that would be useful to further explore the biology of EZH2. © 2012 American Chemical Society. Source

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