NPM and NPM-MLF1 interact with chromatin remodeling complexes and influence their recruitment to specific genes

Nucleophosmin (NPM1) is either frequently mutated or subjected to chromosomal translocation in acute myeloid leukemia (AML). NPM protein is primarily located in the nucleus, but the recurrent NPMc+ mutation is characterized by cytoplasmic localization and leukemogenic properties. Similarly, the NPM-MLF1 translocation product favors the partial cytoplasmic retention of NPM. Regardless of their common cellular distribution, NPM-MLF1 malignancies engender different effects on hematopoiesis compared to NPMc+ counterparts, highlighting possible aberrant nuclear function(s) of NPM in NPMc+ AML. We performed a proteomics analysis and found that NPM and NPM-MLF1 interact with chromatin remodeling complexes of the ISWI family, as well as with NuRD and P/BAF complexes. Accordingly, NPM and NPM-MLF1 are recruited to transcriptionally active or repressed genes along with NuRD and P/BAF elements. Although the overall gene expression program in NPM knockdown cells is similar to that resulting from NPMc+ and is consistent with loss of nuclear function of NPM, NPM-MLF1 expression differentially altered gene transcription regulated by NPM. The abnormal gene regulation imposed by NPM-MLF1 is characterized by enhanced recruitment of NuRD to gene regulatory regions. Thus, different mechanisms orchestrate the deregulation of NPM function in NPMc+- versus NPM1-MLF1-associated leukemia. Gene expression profil was determinated by Ion Ampli Sequencing in K562 sh Scramble (contrôle) and K562 shNPM cells, in triplicate.