Wagstaff M, Sevim O, Goff A, Raynor M, Park H, Mancini E J, Nguyen D T T, Chevassut T, Blair A, Castellano L, Newbury S, Towler B, Morgan R G
School of Life Sciences, University of Sussex, Brighton, UK.
Leeds Institute of Medical Research, Next Generation Sequencing Facility, University of Leeds, Leeds, UK.
Oncogene. 2025 Apr 30. doi: 10.1038/s41388-025-03415-y.
Wnt/β-catenin signalling is important for normal hematopoietic stem/progenitor cell (HSPC) biology and heavily implicated in acute and chronic myeloid leukaemia (AML and CML). The central mediator β-catenin is an attractive therapeutic target in myeloid neoplasms however its targeting has been hampered by a poor characterisation of its molecular interactions in haematopoietic cells, which will differ from its network in solid tissues. Our previous β-catenin interactome study identified the significant enrichment of RNA-binding proteins (RBP) implying post-transcriptional roles for β-catenin in myeloid cells. To identify β-catenin interacting mRNAs we performed β-catenin RNA-immunoprecipitation coupled to RNA-sequencing (RIP-seq) and identified significantly enriched Wnt signalling pathway transcripts. Using β-catenin cross-linking immunoprecipitation (CLIP) we demonstrated a limited capacity for β-catenin to bind RNA directly, implying dependence on other RBPs. β-Catenin was found to interact with Musashi-2 (MSI2) in both myeloid cell lines and primary AML patient samples, where expression was significantly correlated. MSI2 knockdown reduced Wnt signalling output (TCF/LEF activity), through suppression of LEF-1 expression and nuclear localisation. Through both RIP and CLIP we demonstrate MSI2 binds LEF1 mRNA in a partly β-catenin dependent fashion, and may impact the post-transcriptional control of LEF-1 expression. Finally, we show that MSI2-mediated expansion of human HSPCs could be partly driven through LEF1 regulation. This is the first study to experimentally demonstrate functional crosstalk between MSI2 and Wnt signalling in human cells, and indicates potential novel post-transcriptional roles for β-catenin in a haematological context.
Wnt/β-连环蛋白信号通路对正常造血干/祖细胞（HSPC）生物学功能很重要，并且与急性和慢性髓系白血病（AML和CML）密切相关。核心介质β-连环蛋白是髓系肿瘤中一个有吸引力的治疗靶点，然而，由于其在造血细胞中的分子相互作用特征不佳，对其进行靶向治疗受到了阻碍，而这种相互作用与实体组织中的网络不同。我们之前的β-连环蛋白相互作用组研究发现RNA结合蛋白（RBP）显著富集，这意味着β-连环蛋白在髓系细胞中具有转录后作用。为了鉴定与β-连环蛋白相互作用的mRNA，我们进行了β-连环蛋白RNA免疫沉淀结合RNA测序（RIP-seq），并鉴定出显著富集的Wnt信号通路转录本。使用β-连环蛋白交联免疫沉淀（CLIP），我们证明β-连环蛋白直接结合RNA的能力有限，这意味着它依赖于其他RBP。在髓系细胞系和原发性AML患者样本中均发现β-连环蛋白与Musashi-2（MSI2）相互作用，且二者表达显著相关。MSI2敲低通过抑制LEF-1表达和核定位降低了Wnt信号输出（TCF/LEF活性）。通过RIP和CLIP，我们证明MSI2以部分依赖β-连环蛋白的方式结合LEF1 mRNA，并可能影响LEF-1表达的转录后调控。最后，我们表明MSI2介导的人HSPCs扩增可能部分是通过LEF1调控驱动的。这是第一项通过实验证明人细胞中MSI2与Wnt信号通路之间存在功能串扰的研究，并表明β-连环蛋白在血液学背景下可能具有新的转录后作用。
