PML-Retinoic Acid Receptorα Inhibits PML IV Enhancement of PU.1-Induced C/EBP Expression in Myeloid Differentiation.

PML and PU.1 play important roles in myeloid differentiation. PML-deficient mice have an impaired capacity for terminal maturation of their myeloid precursor cells. This finding has been explained, at least in part, by the lack of PML action to modulate retinoic acid-differentiating activities. In this study, we found that C/EBP ε expression is reduced in PML-deficient mice. We showed that PU.1 directly activates the transcription of the C/EBP ε gene that is essential for granulocytic differentiation. The type IV isoform of PML interacted with PU.1, promoted its association with p300, and then enhanced PU.1-induced transcription and granulocytic differentiation. In contrast to PML IV, the leukemia-associated PML-retinoic acid receptor α fusion protein dissociated the PU.1/PML IV/p300 complex and inhibited PU.1-induced transcription. These results suggest a novel pathogenic mechanism of the PML-retinoic acid receptor α fusion protein in acute promyelocytic leukemia. [ABSTRACT FROM AUTHOR]