The Integrity of the Charged Pocket in the BTB/POZ Domain Is Essential for the Phenotype Induced by the Leukemia-Associated t(11;17) Fusion Protein PLZF/RARα

Abstract

Acute myeloid leukemia is characterized by a differentiation block as well as by an increased self-renewal of hematopoietic precursors in the bone marrow. This phenotype is induced by specific acute myeloid leukemia-associated translocations, such as t(15;17) and t(11;17), which involve an identical portion of the retinoic acid receptor A (RARA) and either the promyelocytic leukemia (PML) or promyelocytic zinc finger (PLZF) genes, respectively. The resulting fusion proteins form high molecular weight complexes and aberrantly bind several histone deacetylase-recruiting nuclear corepressor complexes. The amino-terminal BTB/POZ domain is indispensable for the capacity of PLZF to form high molecular weight complexes. Here, we studied the role of dimerization and binding to histone deacetylase-recruiting nuclear corepressor complexes for the induction of the leukemic phenotype by PLZF/RARA and we show that (a) the BTB/POZ domain mediates the oligomerization of PLZF/RARA; (b) mutations that inhibit dimerization of PLZF do the same in PLZF/RARA; (c) the PLZF/RARA-related block of differentiation requires an intact BTB/POZ domain; (d) the mutations interfering with either folding of the BTB/ POZ domain or with its charged pocket prevent the self-renewal of PLZF/RARA-positive hematopoietic stem cells. Taken together, these data provide evidence that the dimerization capacity and the formation of a functionally charged pocket are indispensable for the PLZF/RARA-induced leukemogenesis. (Cancer Res 2005; 65(14): 6080-8)

The PRC1 Polycomb group complex interacts with PLZF/RARA to mediate leukemic transformation

“…Point mutations (D35N-R49Q and Y88A) within the PLZF BTB domain diminish its dimerization properties and abolish the transformation potential of PLZF/RARA (Puccetti et al 2005;Kwok et al 2006). However, these mutations do not perturb its interaction between HDAC and SMRT-NCoR corepressors, suggesting that transformation by PLZF/RARA is not due solely to its interactions with these corepressor complexes.…”

Direct interaction of PU.1 with oncogenic transcription factors reduces its serine phosphorylation and promoter binding

“…20,21 The cDNAs encoding PML, PLZF, PML/RARa, PLZF/RARa, PU.1 and GFP were generated in previous studies. 20 --24 For further sub-cloning of the cDNAs into different expression vectors, the Gateway recombination system (Invitrogen, Darmstadt, Germany) was used.…”

Deacetylase inhibitors modulate proliferation and self-renewal properties of leukemic stem and progenitor cells

“…This observation is consistent with a gradual loss of self-renewing LSC over time and is in agreement with our previous report demonstrating a diminishing replating capacity of PLZF/RARα-positive LSC upon dacinostat treatment. 31 As primary LSC are rare, pathway analysis was performed using transduced IL-3 dependent myeloid 32D cells as a wellaccepted model system. Functional impairment of murine 32D but also of human AML cells was associated with downregulation of c-MYC and BMI1.…”