School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan.
School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan; PhD Program in Medical Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan.
Biochim Biophys Acta Mol Cell Res. 2019 Dec;1866(12):118550. doi: 10.1016/j.bbamcr.2019.118550. Epub 2019 Sep 3.
Alternative splicing (AS) constitutes a pivotal mechanism for expanding the transcriptome and proteome diversity in higher eukaryotes. In contrast, misregulated AS events are relevant to carcinogenic signatures, including migration, angiogenesis, immortality, and drug resistance of cancer cells. Using a transcriptome analysis, discriminative splicing profiles of hypoxia-inducible factor (HIF)-1α transcripts were identified in tumorous tissues compared to adjacent normal tissues of lung cancer (LC) patients. In cancerous tissues or LC-derived cells, relatively high levels of HIF-1α transcripts encoding the HIF-1α isoform were noted compared to adjacent normal tissues and non-cancerous cells. The HIF-1α isoform exhibited a more-prominent effect than that of the HIF-1α isoform translated from HIF-1α transcripts on enhancing promoter activities of the vascular endothelial growth factor receptor 2 (VEGFR2), serine/arginine splicing factor 1 (SRSF1), and c13orf25 genes. An increase in the SRSF1 protein facilitated the generation of HIF-1α transcripts, whereas overexpression of RNA-binding motif protein 4 (RBM4) enhanced the expression of HIF-1α transcripts in the A549 cells. Results of splicing reporter assays demonstrated the differential impacts of RBM4 and SRSF1 on the utilization of HIF-1α exon 14 in a CU element-dependent manner. In addition to transcriptional regulation, overexpression of the HIF-1α and HIF-1α isoforms differentially enhanced the metastatic signatures of A549 cells. Taken together, SRSF1 and RBM4 constitute an antagonistic mechanism on regulating the splicing profiles of HIF-1α gene, which is relevant to the oncogenic signatures of LC cells.
可变剪接（AS）是高等真核生物扩大转录组和蛋白质组多样性的关键机制。相比之下，失调的 AS 事件与致癌特征相关，包括癌细胞的迁移、血管生成、永生和耐药性。通过转录组分析，在肺癌（LC）患者的肿瘤组织与相邻正常组织相比，鉴定出了缺氧诱导因子（HIF）-1α 转录本的有区别的剪接谱。在癌组织或 LC 衍生的细胞中，与相邻正常组织和非癌细胞相比，编码 HIF-1α 同工型的 HIF-1α 转录本的水平相对较高。HIF-1α 同工型比从 HIF-1α 转录本翻译的 HIF-1α 同工型对增强血管内皮生长因子受体 2（VEGFR2）、丝氨酸/精氨酸剪接因子 1（SRSF1）和 c13orf25 基因启动子活性的增强作用更为显著。SRSF1 蛋白的增加促进了 HIF-1α 转录本的产生，而 RNA 结合基序蛋白 4（RBM4）的过表达增强了 A549 细胞中 HIF-1α 转录本的表达。剪接报告基因分析的结果表明，RBM4 和 SRSF1 以 CU 元件依赖的方式对 HIF-1α 外显子 14 的利用产生不同的影响。除了转录调控外，HIF-1α 和 HIF-1α 同工型的过表达还分别增强了 A549 细胞的转移特征。总之，SRSF1 和 RBM4 构成了调节 HIF-1α 基因剪接谱的拮抗机制，与 LC 细胞的致癌特征相关。
