Plumbagin and oridonin reveal new CRM1 binding sites and NES-binding groove features

Abstract

CRM1 is an important drug target in diseases such as cancer and viral infection. Plumbagin and oridonin, the herbal ingredients with known anti-cancer activities, were reported to inhibit CRM1-mediated nuclear export. However, their modes of CRM1 inhibition are unclear. Here, a multi-mutant of yeast CRM1 was engineered to enable the crystallization of these two small molecules in CRM1s NES-binding groove. Each structure showed three inhibitor-binding sites, among which two are conserved in humans. Besides the known binding site, another site also participated in oridonin and plumbagins CRM1 inhibition. While the plumbagin-bound NES groove resembled the NES-bound groove state, the oridonin-bound groove revealed for the first time a more open NES groove, which may potentially improve cargo-loading through a capture-and-tighten mechanism. Our work thus provides a tool for CRM1 inhibitor crystallization, new insights of CRM1-cargo interaction, and a structural basis for further development of these or other CRM1 inhibitors.