NPM and NPM-MLF1 interact with chromatin remodeling complexes and influence their recruitment to specific genes. 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. Overall design: Gene expression profil was determinated by Ion Ampli Sequencing in K562 sh Scramble (contrôle) and K562 shNPM cells, in triplicate.

核仁磷酸蛋白1（Nucleophosmin, NPM1）在急性髓系白血病（acute myeloid leukemia, AML）中常发生突变或染色体易位。NPM蛋白主要定位于细胞核，而复发性NPMc+突变以胞质定位及致白血病特性为典型特征。类似地，NPM-MLF1易位产物可促使NPM部分滞留于细胞质中。尽管二者具有相似的细胞分布特征，但NPM-MLF1相关恶性肿瘤与NPMc+亚型相比，对造血功能的影响存在显著差异，这提示在NPMc+型急性髓系白血病中，NPM可能存在异常的核功能。本研究开展了蛋白质组学分析，发现NPM及NPM-MLF1可与ISWI家族染色质重塑复合物、NuRD复合物及P/BAF复合物发生相互作用。据此，NPM与NPM-MLF1可与NuRD和P/BAF元件一同被招募至转录活跃或转录沉默的基因区域。尽管NPM敲低细胞的整体基因表达程序与NPMc+诱导的表达程序相似，且与NPM核功能丧失的结果一致，但NPM-MLF1的表达对NPM调控的基因转录产生了差异化影响。NPM-MLF1介导的异常基因调控，其典型特征为NuRD被更高效地招募至基因调控区域。因此，在NPMc+相关白血病与NPM1-MLF1相关白血病中，存在不同的机制调控NPM功能的失调。整体实验设计：以K562细胞的shScramble（对照）组与shNPM组为研究对象，采用Ion Ampli Sequencing进行基因表达谱分析，每组设置3次生物学重复。