APL is characterized by a differentiation arrest at the promyelocytic stage and by the specific t(15;17) chromosomal translocation, which fuses the promyelocytic leukemia gene (PML) and the retinoic acid receptor alpha gene (RARA), which together encode the oncogenic PML-RARA fusion protein [2]. The gene discussed is PML; the disease is acute promyelocytic leukemia.