Gene/Protein Disease Symptom Drug Enzyme Compound
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The five human polycomb (Pc) paralog proteins, chromobox homolog (Cbx) 2/4/6/7/8, are a family of chromodomain containing methyllysine reader proteins that are canonical readers of trimethyllysine 27 on histone 3 (H3K27me3). The aberrant expression of the Cbx7 gene is implicated in several cancers including prostate, gastric, thyroid, pancreas, and colon cancer. Previous reports on antagonizing the molecular recognition of Cbx7-H3K27me3 with chemical inhibitors showed an impact on prostate cancer cell lines. We report here on the design, synthesis, and structure-activity relationships of a series of potent peptidomimetic antagonists that were optimized on a trimethyllysine-containing scaffold to target Cbx7. The ligands were characterized using fluorescence polarization (FP) for their binding efficiency and selectivity against the Pc paralog Cbx proteins. The most selective ligand 9, as indicated by the FP data analysis, was further characterized using the isothermal titration calorimetry (ITC). Compound 9 exhibits a 220 nM potency for Cbx7 and exhibits 3.3, 1.8, 7.3 times selective for Cbx7 over Cbx2/4/8 and 28-fold selective over the HP1 family member Cbx1. Our research provides several potent and partially selective inhibitors for Cbx2/4/7 that do not contain trimethyllysine. Our models and binding data suggest that the aromatic cages of Cbx7/Cbx4 can accommodate larger alkyl groups such as diisobutyl substitution on the lysine nitrogen.
ACS Omega 2016 Oct 31
PMID:Structure-Activity Relationships of Cbx7 Inhibitors, Including Selectivity Studies against Other Cbx Proteins. 3002 85

Histone post-translational modifications (PTMs) are crucial for many cellular processes including mitosis, transcription, and DNA repair. The cellular readout of histone PTMs is dependent on both the chemical modification and histone site, and the array of histone PTMs on chromatin is dynamic throughout the eukaryotic life cycle. Accordingly, methods that report on the presence of PTMs are essential tools for resolving open questions about epigenetic processes and for developing therapeutic diagnostics. Reader domains that recognize histone PTMs have shown potential as advantageous substitutes for anti-PTM antibodies, and engineering efforts aimed at enhancing reader domain affinities would advance their efficacy as antibody alternatives. Here we describe engineered chromodomains from Drosophila melanogaster and humans that bind more tightly to H3K9 methylation (H3K9me) marks and result in the tightest reported reader-H3K9me interaction to date. Point mutations near the binding interface of the HP1 chromodomain were screened in a combinatorial fashion, and a triple mutant was found that binds 20-fold tighter than the native scaffold without any loss in PTM-site selectivity. The beneficial mutations were then translated to a human homologue, CBX1, resulting in an even tighter interaction with H3K9me3. Furthermore, we show that these engineered readers (eReaders) increase detection of H3K9me marks in several biochemical assays and outperform a commercial anti-H3K9me antibody in detecting H3K9me-containing nucleosomes in vitro, demonstrating the utility of eReaders to complement antibodies in epigenetics research.
ACS Chem Biol 2020 01 17
PMID:Engineered Reader Proteins for Enhanced Detection of Methylated Lysine on Histones. 3163 30