Synergistic blockade of mitotic exit by two chemical inhibitors of the APC/C

Katharine L. Sackton, Nevena Dimova, Xing Zeng, Wei Tian, Mengmeng Zhang, Timothy B. Sackton, Johnathan Meaders, Kathleen L. Pfaff, Frederic Sigoillot, Hongtao Yu, Xuelian Luo, Randall W. King

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Abstract

Protein machines are multi-subunit protein complexes that orchestrate highly regulated biochemical tasks. An example is the anaphase-promoting complex/cyclosome (APC/C), a 13-subunit ubiquitin ligase that initiates the metaphase-anaphase transition and mitotic exit by targeting proteins such as securin and cyclin B1 for ubiquitin-dependent destruction by the proteasome. Because blocking mitotic exit is an effective approach for inducing tumour cell death, the APC/C represents a potential novel target for cancer therapy. APC/C activation in mitosis requires binding of Cdc20 (ref. 5), which forms a co-receptor with the APC/C to recognize substrates containing a destruction box (D-box). Here we demonstrate that we can synergistically inhibit APC/C-dependent proteolysis and mitotic exit by simultaneously disrupting two protein-protein interactions within the APC/C-Cdc20-substrate ternary complex. We identify a small molecule, called apcin (APC inhibitor), which binds to Cdc20 and competitively inhibits the ubiquitylation of D-box-containing substrates. Analysis of the crystal structure of the apcin-Cdc20 complex suggests that apcin occupies the D-box-binding pocket on the side face of the WD40-domain. The ability of apcin to block mitotic exit is synergistically amplified by co-addition of tosyl-l-arginine methyl ester, a small molecule that blocks the APC/C-Cdc20 interaction. This work suggests that simultaneous disruption of multiple, weak protein-protein interactions is an effective approach for inactivating a protein machine.

Original languageEnglish (US)
Pages (from-to)646-649
Number of pages4
JournalNature
Volume514
Issue number7524
DOIs
StatePublished - Aug 14 2014

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Sackton, K. L., Dimova, N., Zeng, X., Tian, W., Zhang, M., Sackton, T. B., Meaders, J., Pfaff, K. L., Sigoillot, F., Yu, H., Luo, X., & King, R. W. (2014). Synergistic blockade of mitotic exit by two chemical inhibitors of the APC/C. Nature, 514(7524), 646-649. https://doi.org/10.1038/nature13660