环状RNA circARHGAP35在肝癌中的功能及其分子机制研究

Circular RNA is a type of RNA that forms a covalently closed continuous loop. The expression and regulation of circular RNA is abnormal in cancer. The function and mechanism of circular RNA is still largely unknown. We characterized circular RNA transcripts using high-throughput RNA sequencing and bioinformatics analysis from hepatocellular carcinoma (HCC) and matched normal tissues. We found that circular RNA circARHGAP35 derived from the tumor suppressor gene ARHGAP35 was significantly up-regulated in HCC. CircARHGAP35 promoted HCC cell proliferation，migration and invasion, while ARHGAP35 inhibited the migration and invasion of HCC cell obviously. Our results show that circARHGAP35 can encode a new protein which is shorter than ARHGAP35 protein, and circARHGAP35 protein promotes the proliferation and migration of HCC cell. It is also found that HNRNPL can regulate the formation of circARHGAP35, and the content of circARHGAP35 in the exosomes of HCC patients’ serum is higher than that of normal people. This project will further clarify the regulatory role, specific function and molecular mechanism of circARHGAP35 in hepatocellular carcinoma, and provide new ideas and targets for the diagnosis and treatment of liver cancer.

环状RNA是一类具有共价闭合成环结构的RNA分子，在肿瘤中表达调控异常，功能和机制研究尚少。本研究前期对肝癌与癌旁组织进行高通量RNA测序和生物信息分析，发现来源于抑癌基因ARHGAP35的环状RNA（circARHGAP35）在肝癌组织中反而显著上调。circARHGAP35可明显促进肝癌细胞的增殖、迁移和侵袭，而ARHGAP35显著抑制肝癌细胞的迁移侵袭。circARHGAP35可以编码一个截短的新蛋白，促进肝癌细胞的增殖和迁移。此外，发现HNRNPL可以调控circARHGAP35的生物合成，肝癌病人血清外泌体中的circARHGAP35含量比正常人高。本项目将基于前期基础，进一步阐明circARHGAP35在肝癌中的调控作用，其具体功能和分子机制，为肝癌的诊断治疗提供新的思路及候选靶点。

环状RNA是一类具有共价闭合成环结构的RNA分子，大多数环状RNA的功能和具体的分子机制研究还不清楚。在此项目中，我们鉴定了一个促癌的环状RNA-circARHGAP35。circARHGAP35是由抑癌基因ARHGAP35的2号和3号外显子形成的。我们发现环状RNA circARHGAP35和线性的ARHGAP35基因具有相反的表达和功能。circARHGAP35有一个3867 nt长的ORF，编码出一个具有4个FF结构域，不含RhoGAP结构域的蛋白，蛋白的翻译受m6A的调控。分子机制上，circARHGAP35编码的蛋白在细胞核中与TFII-I结合，从而促进肿瘤的进展。RNA结合蛋白HNRNPL促进了circARHGAP35的形成。circARHGAP35与肿瘤病人比较差的预后有关。我们的研究发现了一个促癌的环状RNA, 并且揭示了环状RNA可以通过编码蛋白这一机制来实现癌基因的激活。