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A 1536-well Fluorescence Polarization Assay to Screen for Modulators of the MUSASHI Family of RNA-Binding Proteins

Minuesa, Gerard and Antczak, Christophe and Shum, David and Radu, Constantin and Bhinder, Bhavneet and Li, Yueming and Djaballah, Hakim and Kharas, Michael (2014) A 1536-well Fluorescence Polarization Assay to Screen for Modulators of the MUSASHI Family of RNA-Binding Proteins. Combinatorial Chemistry & High Throughput Screening, 17 (7). pp. 596-609. ISSN 1875-5402

Abstract

RNA-binding proteins (RBPs) can act as stem cell modulators and oncogenic drivers, but have been largely ignored by the pharmaceutical industry as potential therapeutic targets for cancer. The MUSASHI (MSI) family has recently been demonstrated to be an attractive clinical target in the most aggressive cancers. Therefore, the discovery and development of small molecule inhibitors could provide a novel therapeutic strategy. In order to find novel compounds with MSI RNA binding inhibitory activity, we have developed a fluorescence polarization (FP) assay and optimized it for high throughput screening (HTS) in a 1536-well microtiter plate format. Using a chemical library of 6,208 compounds, we performed pilot screens, against both MSI1 and MSI2, leading to the identification of 7 molecules for MSI1, 15 for MSI2 and 5 that inhibited both. A secondary FP dose-response screen validated 3 MSI inhibitors with IC50 below 10μM. Out of the 25 compounds retested in the secondary screen only 8 demonstrated optical interference due to high fluorescence. Utilizing a SYBR-based RNA electrophoresis mobility shift assay (EMSA), we further verified MSI inhibition of the top 3 compounds. Surprisingly, even though several aminoglycosides were present in the library, they failed to demonstrate MSI inhibitor activity challenging the concept that these compounds are pan-active against RBPs. In summary, we have developed an in vitro strategy to identify MSI specific inhibitors using an FP HTS platform, which will facilitate novel drug discovery for this class of RBPs.

Item Type: Article
Date Deposited: 13 Oct 2015 13:12
Last Modified: 04 Jul 2016 23:45
URI: https://oak.novartis.com/id/eprint/22438

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