A negative feedback loop between nuclear factor 90 (NF90) and an anti-oncogenic microRNA, miR-7
A negative feedback loop between nuclear factor 90 (NF90) and an anti-oncogenic microRNA, miR-7
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DOI：
10.1016/j.bbrc.2018.07.119
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发表时间：
2018-09-10
影响因子：
3.1
通讯作者：
Sakamoto, Shuji
中科院分区：
文献类型：
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作者：
Higuchi, Takuma;Morisawa, Keiko;Sakamoto, Shuji
microRNAs （miRNAs）水平的改变与肿瘤发生密切相关。然而，肿瘤中调控miRNA产生的分子机制尚不完全清楚。我们之前报道过，通过双链rna结合蛋白与原代miR-7结合，核因子90 (NF90)-核因子45 （NF45）复合物的过度表达导致miR-7的下调，miR-7是一种抗癌miRNA，从而促进肿瘤发生（Higuchi et al . 2016）。在本研究中，我们发现过表达miR-7可显著降低NF90蛋白水平。有趣的是，mir -7介导的NF90家族蛋白的减少仅在NF90蛋白中观察到，而在NF110蛋白中没有观察到，NF110蛋白是NF90基因的一个较长的形式。荧光素酶报告基因分析表明，过表达miR-7可显著抑制NF90 mRNA编码区含有miR-7预测靶序列的荧光素酶活性。在编码区有一个突变的miR-7靶点的报告载体的荧光素酶活性在对照组和miR-7过表达的细胞中是相同的。此外，没有NF90 mRNA 3'UTR的TARGET标记的NF90 mRNA的翻译被miR-7的过表达抑制。这些结果表明，miR-7通过将miR-7结合到NF90 mRNA编码区种子序列的互补位点，在蛋白水平上抑制NF90。我们进一步证实，在转染了靶向miR-7的反义寡核苷酸的SK-N-SH细胞中，内源性NF90蛋白水平升高，表明miR-7介导的NF90翻译抑制是一种生理事件。结合我们之前的研究结果（Higuchi et al 2016），这表明在生理条件下，肿瘤组织中NF90和miR-7之间的负反馈回路增加了NF90的水平。(C) 2018爱思唯尔公司版权所有。
Alterations in microRNAs (miRNAs) levels deeply correlate with tumorigenesis. However, the molecular mechanism for the regulation of the miRNA production in tumors is not fully understood. We previously reported that downregulation of miR-7, which is an anti-oncogenic miRNA, was caused by over expression of the nuclear factor 90 (NF90)-nuclear factor 45 (NF45) complex through the binding of double-stranded (ds) RNA-binding proteins to primary miR-7, resulting in promotion of tumorigenesis (Higuchi et al 2016). During this study, we found that the level of NF90 protein was dramatically decreased by overexpression of miR-7. Interestingly, the miR-7-mediated reduction in NF90 family proteins was only observed in NF90 protein, but not in NF110 protein, which is a longer form of the NF90 gene. Luciferase reporter analysis indicated that the overexpression of miR-7 significantly repressed the luciferase activity in the coding region of NF90 mRNA harboring a predicted target sequence of miR-7. The luciferase activity of the reporter vector, which has a mutated miR-7 target site in the coding region, was the same in the control and miR-7 overexpressed cells. Furthermore, the translation of TARGET tagged NF90 mRNA without the 3'UTR of the NF90 mRNA was inhibited by the overexpression of miR-7. These results imply that miR-7 suppresses NF90 at the protein level through the binding of miR-7 to the complementary site of the seed sequence in the coding region of the NF90 mRNA. We further confirmed increased endogenous NF90 protein levels in SK-N-SH cells transfected with antisense oligonucleotides targeting miR-7, indicating that miR-7-mediated translational repression of NF90 is a physiological event. Taken together with our previous findings (Higuchi et al 2016), it suggests that the level of NF90 is increased by a negative feedback loop between NF90 and miR-7 in tumor tissues under physiological conditions. (C) 2018 Elsevier Inc. All rights reserved.