Schematic model indicating the downstream function of the FANCD2 protein in the FA/BRCA pathway. Following cellular exposure to DNA damaging agents (IR or MMC, for example), FANCD2 is monoubiquitinated in an FA complex–dependent manner. Monoubiquitinated FANCD2 is then targeted to the chromatin, perhaps by a chromatin targeting factor. The carboxy terminal EDGE region of FANCD2, required for its functional activity (resistance to MMC), may then interact with other downstream proteins involved in DNA repair. Also, the monoubiquitin moiety of FANCD2 may also interact with other chromatin factors(s) containing a ubiquitin binding domain.