Disruption of FAT10–MAD2 binding inhibits tumor progression

Significance FAT10, a ubiquitin-like modifier, is an oncogene that interacts with mitotic arrest-deficient 2 (MAD2) and confers cellular malignancy. Here we identified the MAD2-binding residues of FAT10 and determined the first solution structure, to our knowledge, of the first FAT10 ubiquitin-like domain. Importantly, we demonstrated the proof-of-mechanism for a novel and specific drug-targeting strategy that entails the specific inhibition of the pathological activity of a therapeutic target but not its reported physiological function, thus minimizing undesirable side effects: Abrogation of the FAT10–MAD2 interaction curtailed tumor progression without affecting FAT10’s interaction with its other known physiological binding partners. This study presents a paradigm for drug targeting and paves the way for the development of a novel small-molecule anticancer inhibitor targeting the MAD2-binding interface of FAT10. FAT10 (HLA-F-adjacent transcript 10) is a ubiquitin-like modifier that is commonly overexpressed in various tumors. It was found to play a role in mitotic regulation through its interaction with mitotic arrest-deficient 2 (MAD2). Overexpression of FAT10 promotes tumor growth and malignancy. Here, we identified the MAD2-binding interface of FAT10 to be located on its first ubiquitin-like domain whose NMR structure thus was determined. We further proceeded to demonstrate that disruption of the FAT10–MAD2 interaction through mutation of specific MAD2-binding residues did not interfere with the interaction of FAT10 with its other known interacting partners. Significantly, ablation of the FAT10–MAD2 interaction dramatically limited the promalignant capacity of FAT10, including promoting tumor growth in vivo and inducing aneuploidy, proliferation, migration, invasion, and resistance to apoptosis in vitro. Our results strongly suggest that the interaction of FAT10 with MAD2 is a key mechanism underlying the promalignant property of FAT10 and offer prospects for the development of anticancer strategies.