NOVA1 directs PTBP1 to hTERT pre-mRNA and promotes telomerase activity in cancer cells
NOVA1 directs PTBP1 to hTERT pre-mRNA and promotes telomerase activity in cancer cells
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DOI：
10.1038/s41388-018-0639-8
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发表时间：
2019-04-18
期刊：
影响因子：
8
通讯作者：
Ludlow, Andrew T.
中科院分区：
文献类型：
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作者：
Sayed, Mohammed E.;Yuan, Laura;Ludlow, Andrew T.
癌细胞中的选择性剪接失调，驱动异构体的产生，使肿瘤细胞能够存活并持续增殖。端粒酶重新激活的一部分涉及 hTERT 转录本的剪接以产生全长 (FL) TERT。迄今为止，很少有剪接因子被描述为与 hTERT 相互作用并促进 FL TERT 的产生。我们最近描述了一种这样的剪接因子 NOVA1，它作为 FL hTERT 剪接的增强子，增加端粒酶活性，并促进癌细胞中端粒的维持。 NOVA1 主要在神经元中表达并参与神经发生。在目前的研究中，我们描述了通常也参与神经发生的多聚嘧啶束结合蛋白（PTBP）也参与癌症中 hTERT 与 FL 的剪接。癌细胞中 PTBP1 的敲除实验表明 PTBP1 降低 hTERT FL 剪接和端粒酶活性。 PTBP1 的稳定敲低导致 H1299 和 H920 肺癌细胞中端粒长度逐渐缩短。 RNA Pulldown 实验表明 PTBP1 以 NOVA1 依赖性方式与 hTERT 前体 mRNA 相互作用。 PTBP1 的敲低会增加 PTBP2 的表达，PTBP2 也与 NOVA1 相互作用，可能阻止 NOVA1 与 hTERT 前体 mRNA 的关联。这些新数据强调癌细胞中的剪接是通过剪接位点的竞争来调节的，并且剪接因子的组合在前mRNA转录本上的顺式调节位点上相互作用。通过使用 hTERT 作为模型基因，我们通过调节在绝大多数癌细胞类型中表达的端粒酶，展示了剪接因子 NOVA1 和 PTBP1 在癌症中的协调作用。
Alternative splicing is dysregulated in cancer cells, driving the production of isoforms that allow tumor cells to survive and continuously proliferate. Part of the reactivation of telomerase involves the splicing of hTERT transcripts to produce full-length (FL) TERT. Very few splicing factors to date have been described to interact with hTERT and promote the production of FL TERT. We recently described one such splicing factor, NOVA1, that acts as an enhancer of FL hTERT splicing, increases telomerase activity, and promotes telomere maintenance in cancer cells. NOVA1 is expressed primarily in neurons and is involved in neurogenesis. In the present studies, we describe that polypyrimidine-tract binding proteins (PTBPs), which are also typically involved in neurogenesis, are also participating in the splicing of hTERT to FL in cancer. Knockdown experiments of PTBP1 in cancer cells indicate that PTBP1 reduces hTERT FL splicing and telomerase activity. Stable knockdown of PTBP1 results in progressively shortened telomere length in H1299 and H920 lung cancer cells. RNA pulldown experiments reveal that PTBP1 interacts with hTERT pre-mRNA in a NOVA1 dependent fashion. Knockdown of PTBP1 increases the expression of PTBP2 which also interacts with NOVA1, potentially preventing the association of NOVA1 with hTERT pre-mRNA. These new data highlight that splicing in cancer cells is regulated by competition for splice sites and that combinations of splicing factors interact at cis regulatory sites on pre-mRNA transcripts. By employing hTERT as a model gene, we show the coordination of the splicing factors NOVA1 and PTBP1 in cancer by regulating telomerase that is expressed in the vast majority of cancer cell types.