Using Acute Promyelocytic Leukemia (APL) to Study the PML-associated Daxx/ATRX Complex and Its Role in Pediatric Malignancies

Abstract

Using NB4 cells as a tool we have studied the PML-associated Daxx/ATRX (PAX) complex. As its constituents play a role in cancer, many of the novel components identified here may represent promising novel drug targets for cancer therapy. Using the BioID method, we have defined dynamics of the interactome of the Daxx/ATRX complex, which will be an invaluable resource for further studies. The Mass-spec results of the pull-down experiments using ATRA-treated NB4-BD and NB4-SB1 sublines, revealed SMCHD1 strongly suggest that SMCHD1 is a novel interactors of the PML-associated Daxx/ATRX complex. Our pull-down experiments also identified SMARCA4 (also called BRG1) as a Daxx interactor. We confirmed this interaction both in vitro and in cells by performing Daxx-SMARCA4 Co-IP and FRET experiments. Moreover, the results of our 4-OH TXF-induced SMARCA4 knockout experiments indicated the dependency of cells immortalized by various oncogenes on SMARCA4 for their proliferation. We believe that finding novel inhibitors and/or seeking for alternative methods to inhibit SMARCA4 are still a promising approach for novel cancer therapeutics.