A MHC-encoded ubiquitin-like protein (FAT10) binds noncovalently to the spindle assembly checkpoint protein MAD2

Recently a number of nonclass I genes were discovered in the human MHC clas s I region. One of these, FAT10, encodes a protein consisting of two domain s with homology to ubiquitin. FAT10 mRNA is expressed constitutively in som e lymphoblastoid lines and dendritic cells and in certain other cells after gamma-interferon induction. FAT10 protein expression is controlled at seve ral levels including transcription, translation, and protein stability. Yea st two-hybrid screening of a human lymphocyte library and immunoprecipitati on studies revealed that FAT10 noncovalently associated with MAD2, a protei n implicated in a cell-cycle checkpoint for spindle assembly during anaphas e. Thus, FAT10 may modulate cell growth during B cell or dendritic cell dev elopment and activation.