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An intrinsically labile α-helix abutting the BCL9-binding site of β-catenin is required for its inhibition by carnosic acid.

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Rutherford, Trevor J 
Gupta, Deepti 
Veprintsev, Dmitry B 
Saxty, Barbara 


Wnt/β-catenin signalling controls development and tissue homeostasis. Moreover, activated β-catenin can be oncogenic and, notably, drives colorectal cancer. Inhibiting oncogenic β-catenin has proven a formidable challenge. Here we design a screen for small-molecule inhibitors of β-catenin's binding to its cofactor BCL9, and discover five related natural compounds, including carnosic acid from rosemary, which attenuates transcriptional β-catenin outputs in colorectal cancer cells. Evidence from NMR and analytical ultracentrifugation demonstrates that the carnosic acid response requires an intrinsically labile α-helix (H1) amino-terminally abutting the BCL9-binding site in β-catenin. Similarly, in colorectal cancer cells with hyperactive β-catenin signalling, carnosic acid targets predominantly the transcriptionally active ('oncogenic') form of β-catenin for proteasomal degradation in an H1-dependent manner. Hence, H1 is an 'Achilles' Heel' of β-catenin, which can be exploited for destabilization of oncogenic β-catenin by small molecules, providing proof-of-principle for a new strategy for developing direct inhibitors of oncogenic β-catenin.



Abietanes, Binding Sites, Cell Line, Tumor, Colorectal Neoplasms, Crystallography, X-Ray, HEK293 Cells, HeLa Cells, Humans, Neoplasm Proteins, Nuclear Magnetic Resonance, Biomolecular, Plant Extracts, Proteasome Endopeptidase Complex, Protein Stability, Rosmarinus, Signal Transduction, Transcription Factors, Wnt Proteins, beta Catenin

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Nat Commun

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Springer Science and Business Media LLC