Disease-linked microRNA-21 exhibits drastically reduced mRNA binding and silencing activity in healthy mouse liver
Disease-linked microRNA-21 exhibits drastically reduced mRNA binding and silencing activity in healthy mouse liver
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DOI：
10.1261/rna.033308.112
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发表时间：
2012-08-01
期刊：
影响因子：
4.5
通讯作者：
Walter, Nils G.
中科院分区：
文献类型：
--
作者：
Androsavich, John R.;Chau, B. Nelson;Walter, Nils G.
microRNAs（miRNAs）与mRNA结合，通过影响mRNA的稳定性和/或翻译来微调蛋白质输出。miR-21是一种普遍存在的、高度丰富的应激反应性miRNA，与多种疾病相关，包括癌症、纤维化和炎症。虽然miR-21在患病细胞中的RNA沉默活性已被充分记录，但miR-21在健康细胞条件下的作用尚未得到充分理解。在这里，我们表明，健康小鼠肝脏中miR-21的药理学抑制或遗传缺失对经典种子匹配mRNA的调节几乎没有影响，并且只有有限数量的基因富集在应激反应途径中。这些对已知和预测的靶mRNA的令人惊讶的微弱和选择性调节作用与其他丰富的肝脏miRNA如miR-122和let-7的作用形成对比。此外，与miR-122和let-7相比，miR-21显示与多核糖体相关的靶mRNA的结合大大降低。生物信息学分析表明，种子配对和靶标结合的热力学稳定性降低可能导致miR-21的这种缺陷。值得注意的是，这些趋势在人宫颈癌（HeLa）细胞中被逆转，其中包括miR-21的miRNA在多核糖体内显示增强的靶结合，并且其中miR-21触发对靶mRNA的强降解活性。综上所述，我们的结果表明，在肝脏中的正常细胞条件下，miR-21活性维持在结合和沉默其大多数靶点所需的阈值以下。因此，与多核糖体相关mRNA的增强关联可能部分解释了通常在患病或应激细胞中发现的miR-21功能的获得。
MicroRNAs (miRNAs) bind to mRNAs and fine-tune protein output by affecting mRNA stability and/or translation. miR-21 is a ubiquitous, highly abundant, and stress-responsive miRNA linked to several diseases, including cancer, fibrosis, and inflammation. Although the RNA silencing activity of miR-21 in diseased cells has been well documented, the roles of miR-21 under healthy cellular conditions are not well understood. Here, we show that pharmacological inhibition or genetic deletion of miR-21 in healthy mouse liver has little impact on regulation of canonical seed-matched mRNAs and only a limited number of genes enriched in stress response pathways. These surprisingly weak and selective regulatory effects on known and predicted target mRNAs contrast with those of other abundant liver miRNAs such as miR-122 and let-7. Moreover, miR-21 shows greatly reduced binding to polysome-associated target mRNAs compared to miR-122 and let-7. Bioinformatic analysis suggests that reduced thermodynamic stability of seed pairing and target binding may contribute to this deficiency of miR-21. Significantly, these trends are reversed in human cervical carcinoma (HeLa) cells, where miRNAs including miR-21 show enhanced target binding within polysomes and where miR-21 triggers strong degradative activity toward target mRNAs. Taken together, our results suggest that, under normal cellular conditions in liver, miR-21 activity is maintained below a threshold required for binding and silencing most of its targets. Consequently, enhanced association with polysome-associated mRNA is likely to explain in part the gain of miR-21 function often found in diseased or stressed cells.