Department of Biomedical Sciences, University of Ulsan College of Medicine, Asan Medical Center, Seoul, 05505, Korea.
Rare Disease Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Korea.
Dig Dis Sci. 2018 Jul;63(7):1835-1850. doi: 10.1007/s10620-018-5081-9. Epub 2018 Apr 25.
Adenosine deaminase acting on RNA 1 (ADAR1) is known to mediate deamination of adenosine-to-inosine through binding to double-stranded RNA, the phenomenon known as RNA editing. Currently, the function of ADAR1 in gastric cancer is unclear.
This study was aimed at investigating RNA editing-dependent and editing-independent functions of ADAR1 in gastric cancer, especially focusing on its influence on editing of 3' untranslated regions (UTRs) and subsequent changes in expression of messenger RNAs (mRNAs) as well as microRNAs (miRNAs).
RNA-sequencing and small RNA-sequencing were performed on AGS and MKN-45 cells with a stable ADAR1 knockdown. Changed frequencies of editing and mRNA and miRNA expression were then identified by bioinformatic analyses. Targets of RNA editing were further validated in patients' samples.
In the Alu region of both gastric cell lines, editing was most commonly of the A-to-I type in 3'-UTR or intron. mRNA and protein levels of PHACTR4 increased in ADAR1 knockdown cells, because of the loss of seed sequences in 3'-UTR of PHACTR4 mRNA that are required for miRNA-196a-3p binding. Immunohistochemical analyses of tumor and paired normal samples from 16 gastric cancer patients showed that ADAR1 expression was higher in tumors than in normal tissues and inversely correlated with PHACTR4 staining. On the other hand, decreased miRNA-148a-3p expression in ADAR1 knockdown cells led to increased mRNA and protein expression of NFYA, demonstrating ADAR1's editing-independent function.
ADAR1 regulates post-transcriptional gene expression in gastric cancer through both RNA editing-dependent and editing-independent mechanisms.
腺苷脱氨酶作用于 RNA1（ADAR1）已知通过结合双链 RNA 介导腺苷脱氨酶到肌苷的脱氨作用，这种现象称为 RNA 编辑。目前，ADAR1 在胃癌中的功能尚不清楚。
本研究旨在探讨 ADAR1 在胃癌中的 RNA 编辑依赖和非编辑依赖功能，特别是其对 3'非翻译区（UTR）编辑的影响以及随后信使 RNA（mRNA）和 microRNA（miRNA）表达的变化。
对具有稳定 ADAR1 敲低的 AGS 和 MKN-45 细胞进行 RNA-seq 和 small RNA-seq。然后通过生物信息学分析鉴定编辑和 mRNA 和 miRNA 表达变化的频率。在患者样本中进一步验证 RNA 编辑的靶标。
在两种胃细胞系的 Alu 区域，编辑最常见的是 3'-UTR 或内含子中的 A 到 I 类型。由于 PHACTR4 mRNA 3'-UTR 中需要 miRNA-196a-3p 结合的种子序列丢失，ADAR1 敲低细胞中 PHACTR4 的 mRNA 和蛋白水平增加。对 16 例胃癌患者的肿瘤和配对正常样本进行免疫组织化学分析显示，ADAR1 表达在肿瘤中高于正常组织，与 PHACTR4 染色呈负相关。另一方面，ADAR1 敲低细胞中 miRNA-148a-3p 表达减少导致 NFYA 的 mRNA 和蛋白表达增加，表明 ADAR1 具有非编辑依赖的功能。
ADAR1 通过 RNA 编辑依赖和非编辑依赖机制调节胃癌中的转录后基因表达。
