FAT10 is a ubiquitin-like protein discovered by chromosmal sequencing in the human MHC class I locus. The protein consists of two ubiquitin-like domains in a head-to-tail arrangement and contains a C-terminal di-glycine which is critical for covalent conjugation to target proteins. FAT10 expression is inducible by the IFN-γ and TNF-α cytokines, and it may modulate tumorigenesis through its reported interaction with the MAD2 spindle-assembly checkpoint protein. Proteins conjugated to FAT10 are rapidly degraded by the proteasome.