LIN28B alters ribosomal dynamics to promote metastasis in MYCN-driven malignancy (Polysome sequencing)

High expression of LIN28B is associated with aggressive malignancy and poor survival. Here, probing MYCN-amplified neuroblastoma as a model system, we show that LIN28B expression is associated with enhanced cell migration in vitro and invasive and metastatic behavior in murine xenografts. Sequence analysis of the polyribosome fraction of LIN28B-expressing neuroblastoma cells revealed let-7 independent enrichment of transcripts encoding components of the translational and ribosomal apparatus, particularly those with higher adenine/uridine (AU)-content, and depletion of transcripts of neuronal developmental programs. We further show that LIN28B utilizes both its cold shock and zinc finger RNA binding domains to preferentially interact with MYCN-induced transcripts of the ribosomal complex, enhancing their translation. These data demonstrate that LIN28B couples the MYCN-driven transcriptional program to enhanced ribosomal translation, thereby implicating LIN28B as a post-transcriptional driver of the metastatic phenotype. Comparison of LIN28B WT BE2C versus LIN28B KO BE2C cells with polysome sequencing.

LIN28B高表达与侵袭性恶性肿瘤及不良预后显著相关。本研究以MYCN扩增型神经母细胞瘤作为模型系统，研究结果显示，LIN28B表达可增强神经母细胞瘤细胞的体外迁移能力，并促进小鼠异种移植模型中的侵袭与转移行为。对表达LIN28B的神经母细胞瘤细胞的多聚核糖体组分进行序列分析后发现，在不依赖let-7的情况下，编码翻译系统与核糖体装置组分的转录本发生显著富集，尤以腺嘌呤/尿嘧啶（AU）含量较高的转录本为甚；同时神经元发育程序相关转录本则出现耗竭。我们进一步证实，LIN28B可通过其冷休克结构域与锌指RNA结合结构域，优先结合MYCN诱导的核糖体复合物转录本，进而增强其翻译效率。上述数据表明，LIN28B可将MYCN驱动的转录程序与增强的核糖体翻译过程相耦联，由此提示LIN28B是转移表型的转录后驱动因子。本研究通过多聚核糖体测序，对LIN28B野生型BE2C细胞与LIN28B基因敲除型BE2C细胞开展了对比分析。