The first clue that the SLX4 UBZ4 domains were physiologically relevant came from identifying Fanconi anemia patients carrying in-frame deletions of SLX4 that disrupted UBZ-1 and deleted UBZ-2 (Kim et al., 2011; Stoepker et al., 2011). The gene discussed is SLX4; the disease is Fanconi anemia.