The t(15;17) translocation, specifically associated with the human acute promyelocytic leukemia (APL), fuses the retinoic acid receptor alpha (RAR alpha) to a novel gene PML generating the hybrid protein PML-RAR.     ///    This observation suggested that the changes in the myeloblastin regulation by RA found in NB4 cells could be ascribed to the presence of the fusion protein PML-RAR. 