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Abstract：
Processing of the eukaryotic transcriptome is a dynamic regulatory mechanism that confers genetic diversity, and splicing and adenosine to inosine (A-to-I) RNA editing are well-characterized examples of such processing. Growing evidence reveals the cross-talk between the splicing and RNA editing, but there is a paucity of substantial evidence for its mechanistic details and contribution in a physiological context. Here, our findings demonstrate that tumor-associated differential RNA editing, in conjunction with splicing machinery, regulates the expression of variants of HNRPLL, a gene encoding splicing factor. We discovered an HNRPLL transcript variant containing an additional exon 12A (E12A), which is a substrate of ADAR1 and ADAR2. Adenosine deaminases acting on RNA (ADAR) direct deaminase-dependent expression of the E12A transcript, and ADAR-mediated regulation of E12A is largely splicing-based, and does not affect the stability or nucleocytoplasmic distribution of the transcript. Furthermore, ADAR-mediated modification of exon 12A generates an enhancer for the oncogenic splicing factor SRSF1 and consequently promotes the frequency of alternative splicing. Gene expression profiling by RNA-seq revealed that E12A acts distinctly from HNRPLL and regulates a set of growth-related genes, such as cyclin CCND1 and growth factor receptor TGFBR1 Accordingly, silencing E12A expression leads to impaired clonogenic ability and enhanced sensitivity to doxorubicin, thus highlighting the significance of this alternative isoform in tumor cell survival. In summary, we present the interplay of RNA editing and splicing as a regulatory mechanism of gene expression and also its physiological relevance. These findings extend our understanding of transcriptional dynamics and provide a mechanistic explanation to the link of RNA editors to tumorigenesis.
摘要：
真核转录组的加工是赋予遗传多样性的动态调节机制，剪接和腺苷到肌苷(A到I)RNA编辑是此类加工的充分表征的实例。越来越多的证据揭示了剪接和RNA编辑之间的交叉对话，但是缺乏大量证据证明其在生理背景下的机械细节和贡献。这里,我们的发现表明，肿瘤相关的差异RNA编辑，结合拼接机械，调节HNRPLL变体的表达，编码剪接因子的基因。我们发现了一个含有额外外显子12A（E12A）的HNRPLL转录变体，它是ADAR1和ADAR2的底物。腺苷脱氨酶作用于E12A转录物的RNA（ADAR）直接脱氨酶依赖性表达，ADAR介导的E12A调控主要是基于剪接，并且不影响转录物的稳定性或核质分布。此外，ADAR介导的外显子12A的修饰产生致癌剪接因子SRSF1的增强子,并因此促进选择性剪接的频率。通过RNA-seq的基因表达谱显示，E12A与HNRPLL的作用明显不同，并调节一组与生长相关的基因，如细胞周期蛋白CCND1和生长因子受体TGFBR1，沉默E12A表达导致克隆形成能力受损，并增强对阿霉素的敏感性，从而突出了这种替代同工型在肿瘤细胞存活中的重要性。总之,我们提出了RNA编辑和剪接的相互作用作为基因表达的调节机制及其生理相关性。这些发现扩展了我们对转录动力学的理解，并为RNA编辑与肿瘤发生的联系提供了机械解释。
