Leukemia-associated retinoic acid receptor alpha fusion partners, PML and PLZF, heterodimerize and colocalize to nuclear bodies

In acute promyelocytic leukemia (APL), the typical t(15;17) and the rare t(11;17) translocations express, respectively, the PML/RAR alpha and PLZF/RAR alpha fusion proteins (where RAR alpha is retinoic acid receptor alpha). Herein, we demonstrate that the PLZF and PML proteins interact,vith each other and colocalize onto nuclear bodies (NBs), Furthermore, induction of PML expression by interferons leads to a recruitment of PLZF onto NBs without increase in the levels of the PLZF protein, PML/RAR alpha and PLZF/RAR alpha localize to the same microspeckled nuclear domains that appear to be common targets for the two fusion proteins in APL, Although PLZF/RAR alpha does not affect the localization of PML, PML/RAR alpha delocalizes the endogenous PLZF protein in t(15;17)-positive NB4 cells, pointing to a hierarchy in the nuclear targeting of these proteins, Thus, our results unify the molecular pathogenesis of APL with at least two different RAR alpha gene translocations and stress the importance of alterations of PLZF and RAR alpha nuclear localizations in this disease.