a College of Animal Science , South China Agricultural University , Guangzhou , P. R. China.
b Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding & Key Laboratory of Chicken Genetics, Breeding and Reproduction , Ministry of Agriculture , Guangzhou , P. R. China.
RNA Biol. 2019 Jan;16(1):118-132. doi: 10.1080/15476286.2018.1564462. Epub 2019 Jan 15.
Circular RNAs (circRNAs) are evolutionarily conserved and widely present, but their functions remain largely unknown. Recent development has highlighted the importance of circRNAs as the sponge of microRNA (miRNA) in cancer. We previously reported that gga-miR-375 was downregulated in the liver tumors of chickens infected with avian leukosis virus subgroup J (ALV-J) by microRNA microarray assay. It can be reasonably assumed in accordance with previous studies that the gga-miR-375 may be related to circRNAs. However, the question as to which circRNA acts as the sponge for gga-miR-375 remains to be answered. In this study, circRNA sequencing results revealed that a circRNA Vav3 termed circ-Vav3 was upregulated in the liver tumors of chickens infected with ALV-J. In addition, RNA immunoprecipitation (RIP), biotinylated RNA pull-down and RNA-fluorescence in situ hybridization (RNA-FISH) experiments were conducted to confirm that circ-Vav3 serves as the sponge of gga-miR-375. Furthermore, we confirmed through dual luciferase reporter assay that YAP1 is the target gene of gga-miR-375. The effect of the sponge function of circ-Vav3 on its downstream genes has been further verified by our conclusion that the sponge function of circ-Vav3 can abrogate gga-miR-375 target gene YAP1 and increase the expression level of YAP1. We further confirmed that the circ-Vav3/gga-miR-375/YAP1 axis induces epithelial-mesenchymal transition (EMT) through influencing EMT markers to promote tumorigenesis. Finally, clinical ALV-J-induced tumor livers were collected to detect core gene expression levels to provide a proof to the concluded tumorigenic mechanism. Together, our results suggest that circ-Vav3/gga-miR-375/YAP1 axis is another regulator of tumorigenesis.
环状 RNA（circRNAs）在进化上保守且广泛存在，但它们的功能仍知之甚少。最近的研究强调了 circRNAs 作为癌症中 microRNA（miRNA）海绵的重要性。我们之前通过 microRNA 微阵列分析报告，gga-miR-375 在感染禽白血病病毒亚群 J（ALV-J）的鸡肝脏肿瘤中下调。根据以前的研究，可以合理地假设 gga-miR-375 可能与 circRNAs 有关。然而，作为 gga-miR-375 海绵的 circRNA 是哪一种仍有待回答。在这项研究中，circRNA 测序结果表明，一种名为 circ-Vav3 的 circRNA 在感染 ALV-J 的鸡肝脏肿瘤中上调。此外，进行了 RNA 免疫沉淀（RIP）、生物素标记 RNA 下拉和 RNA 荧光原位杂交（RNA-FISH）实验，以证实 circ-Vav3 是 gga-miR-375 的海绵。此外，通过双荧光素酶报告基因实验证实，YAP1 是 gga-miR-375 的靶基因。通过我们的结论进一步验证了 circ-Vav3 的海绵功能对其下游基因的影响，即 circ-Vav3 的海绵功能可以消除 gga-miR-375 靶基因 YAP1 并增加 YAP1 的表达水平。我们进一步证实，circ-Vav3/gga-miR-375/YAP1 轴通过影响 EMT 标志物诱导上皮-间充质转化（EMT），从而促进肿瘤发生。最后，收集了临床 ALV-J 诱导的肿瘤肝脏来检测核心基因表达水平，为得出的肿瘤发生机制提供了证据。总之，我们的研究结果表明，circ-Vav3/gga-miR-375/YAP1 轴是另一种肿瘤发生的调节剂。
