The promyelocytic leukemia (PML) gene was originally identified in acute promyelocytic leukemia (APL) where it is fused to the retinoic acid receptor alpha (RARA) gene as a result of a t(15; 17) chromosomal translocation (de The et al., 1991; Kakizuka et al., 1991; Pandolfi et al., 1991). Here, RARA is linked to acute promyelocytic leukemia.