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Multiple Synthetic Routes to the Mini-Protein Omomyc and Coiled-Coil Domain Truncations

By Brown Zachary Z; Mapelli Claudio; McCracken Amy Bittner; Chen Kuanchang; Zhu Xiaohong; Garbaccio Robert M; Walji Abbas; Farasat Iman; Shoultz Alycia V; Canada Keith A; et al
From The Journal of organic chemistry (2020), 85(3), 1466-1475, Language: English, Database: MEDLINE

The Myc transcription factor represents an “undruggable” target of high biological interest due to its central role in various cancers. An abbreviated form of the c-Myc protein, called Omomyc, consists of the Myc DNA-binding domain and a coiled-coil region to facilitate dimerization of the 90 amino acid polypeptide. Here we present our results to evaluate the synthesis of Omomyc using three complementary strategies: linear Fmoc solid-phase peptide synthesis (SPPS) using several advancements for difficult sequences, native chemical ligation from smaller peptide fragments, and a high-throughput bacterial expression and assay platform for rapid mutagenesis. This multifaceted approach allowed access to up to gram quantities of the mini-protein and permitted in vitro and in vivo SAR exploration of this modality. DNA-binding results and cellular activity confirm that Omomyc and analogues presented here, are potent binders of the E-box DNA engaged by Myc for transcriptional activation and that this 90-amino acid mini-protein is cell permeable and can inhibit proliferation of Myc-dependent cell lines. We also present additional results on covalent homodimerization through disulfide formation of the full-length mini-protein and show the coiled-coil region can be truncated while preserving both DNA binding and cellular activity. Altogether, our results highlight the ability of advanced peptide synthesis to achieve SAR tractability in a challenging synthetic modality.




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