Covalent-Fragment Screening of BRD4 Identifies a Ligandable Site Orthogonal to the Acetyl-Lysine Binding Sites
| Autor: | Shifali Shishodia, Stefan G. Kathman, Daniel J. Sprague, Michael D. Olp, Steven B. Summers, Brian C. Smith, Sarah L. Wynia-Smith, Alexander V. Statsyuk, Ziyang Xu, Christopher J. Goetz |
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| Rok vydání: | 2020 |
| Předmět: |
0301 basic medicine
BRD4 Alkylation Stereochemistry Lysine Cell Cycle Proteins chemical and pharmacologic phenomena 01 natural sciences Biochemistry Article Small Molecule Libraries 03 medical and health sciences Protein Domains Humans Amino Acid Sequence Cysteine Epigenetics Binding site Binding Sites 010405 organic chemistry Chemistry hemic and immune systems General Medicine 0104 chemical sciences Bromodomain Molecular Docking Simulation HEK293 Cells 030104 developmental biology Covalent bond Molecular Medicine K562 Cells Sequence Alignment Protein Binding Transcription Factors |
| Zdroj: | ACS Chem Biol |
| ISSN: | 1554-8937 1554-8929 |
| DOI: | 10.1021/acschembio.0c00058 |
| Popis: | BRD4, a member of the bromodomain and extraterminal domain (BET) family, has emerged as a promising epigenetic target in cancer and inflammatory disorders. All reported BET family ligands bind within the bromodomain acetyl-lysine binding sites and competitively inhibit BET protein interaction with acetylated chromatin. Alternative chemical probes that act orthogonally to the highly-conserved acetyl-lysine binding sites may exhibit selectivity within the BET family and avoid recently reported toxicity in clinical trials of BET bromodomain inhibitors. Here, we report the first identification of a ligandable site on a bromodomain outside the acetyl-lysine binding site. Inspired by our computational prediction of hotspots adjacent to nonhomologous cysteine residues within the C-terminal BRD4 bromodomain (BRD4-BD2), we performed a midthroughput mass spectrometry screen to identify cysteine-reactive fragments that covalently and selectively modify BRD4. Subsequent mass spectrometry, NMR, and computational docking analyses of electrophilic fragment hits revealed a novel ligandable site near Cys356 that is unique to BRD4 among human bromodomains. This site is orthogonal to the BRD4-BD2 acetyl-lysine binding site as Cys356 modification did not impact binding of the pan-BET bromodomain inhibitor JQ1 in fluorescence polarization assays nor an acetylated histone peptide in AlphaScreen assays. Finally, we tethered our top-performing covalent fragment to JQ1 and performed NanoBRET assays to provide proof of principle that this orthogonal site can be covalently targeted in intact human cells. Overall, we demonstrate the potential of targeting sites orthogonal to bromodomain acetyl-lysine binding sites to develop bivalent and covalent inhibitors that displace BRD4 from chromatin. |
| Databáze: | OpenAIRE |
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