RNA. 2013 Nov;19(11):1525-36. doi: 10.1261/rna.041533.113. Epub 2013 Sep 25.
Rho GTPase activating protein 26 (ARHGAP26) is a negative regulator of the Rho family that converts the small G proteins RhoA and Cdc42 to their inactive GDP-bound forms. It is essential for the CLIC/GEEC endocytic pathway, cell spreading, and muscle development. The present study shows that ARHGAP26 mRNA undergoes extensive A-to-I RNA editing in the 3' UTR that is specifically catalyzed by ADAR1. Furthermore, the mRNA and protein levels of ARHGAP26 were decreased in cells in which ADAR1 was knocked down. Conversely, ADAR1 overexpression increased the abundance of ARHGAP26 mRNA and protein. In addition, we found that both miR-30b-3p and miR-573 target the ARHGAP26 gene and that RNA editing of ARHGAP26 mediated by ADAR1 abolished the repression of its expression by miR-30b-3p or miR-573. When ADAR1 was overexpressed, the reduced abundance of ARHGAP26 protein mediated by miR-30b-3p or miR-573 was rescued. Importantly, we also found that knocking down ADAR1 elevated RhoA activity, which was consistent with the reduced level of ARHGAP26. Conversely, when ADAR1 was overexpressed, the amount of RhoA-GTP decreased. The similar expression patterns of ARHGAP26 and ADAR1 in human tissue samples further confirmed our findings. Taken together, our results suggest that ADAR1 regulates the expression of ARHGAP26 through A-to-I RNA editing by disrupting the binding of miR-30b-3p and miR-573 within the 3' UTR of ARHGAP26. This study provides a novel insight into the mechanism by which ADAR1 and its RNA editing function regulate microRNA-mediated modulation of target genes.
Rho GTPase 激活蛋白 26（ARHGAP26）是 Rho 家族的负调控因子，可将小 G 蛋白 RhoA 和 Cdc42 转化为其非活性 GDP 结合形式。它是 CLIC/GEEC 内吞途径、细胞扩展和肌肉发育所必需的。本研究表明，ARHGAP26 mRNA 在 3'UTR 中经历广泛的 A-to-I RNA 编辑，该编辑由 ADAR1 特异性催化。此外，在 ADAR1 敲低的细胞中，ARHGAP26 mRNA 和蛋白水平降低。相反，ADAR1 过表达增加了 ARHGAP26 mRNA 和蛋白的丰度。此外，我们发现 miR-30b-3p 和 miR-573 均可靶向 ARHGAP26 基因，并且 ADAR1 介导的 ARHGAP26 RNA 编辑消除了 miR-30b-3p 或 miR-573 对其表达的抑制作用。当 ADAR1 过表达时，miR-30b-3p 或 miR-573 介导的 ARHGAP26 蛋白丰度降低得到挽救。重要的是，我们还发现敲低 ADAR1 会增加 RhoA 活性，这与 ARHGAP26 水平降低一致。相反，当 ADAR1 过表达时，RhoA-GTP 的量减少。人类组织样本中 ARHGAP26 和 ADAR1 的相似表达模式进一步证实了我们的发现。总之，我们的研究结果表明，ADAR1 通过破坏 miR-30b-3p 和 miR-573 在 ARHGAP26 3'UTR 中的结合，通过 A-to-I RNA 编辑来调节 ARHGAP26 的表达。本研究为 ADAR1 及其 RNA 编辑功能通过干扰 microRNA 对靶基因的调节来调节机制提供了新的见解。
