Since the discovery of the PML gene as a fusion partner with retinoic acid receptor (RAR) α in the t(15:17) chromosomal translocation associated with acute promyelocytic leukemia (APL) [1]–[3], nuclear PML protein has been implicated in a number of cellular processes ranging from cell growth and tumor suppression, to apoptosis, transcriptional regulation, chromatin remodeling, DNA repair, and anti-viral defense [4]–[8]. This evidence concerns the gene PML and acute promyelocytic leukemia.