FANCD2 and Friedreich ataxia: Loss-of-function mutations of USP1, the FANCD2/FANCIdeubiquitinase, result in an FA-like phenotype in a mouse model and in human cells.Indeed, to be unable to monoubiquitinate FANCD2 or to have FANCD2 constitutivelymonoubiquitinated represents a similarly poor fate for a cell.