Department of Entomology, The Hebrew University, Rehovot 76100, Israel.
RNA. 2012 Nov;18(11):1947-56. doi: 10.1261/rna.032185.111. Epub 2012 Sep 27.
MicroRNAs (miRNAs) are short, single-stranded RNAs that silence gene expression by either degrading mRNA or repressing translation. Each miRNA regulates a specific set of mRNA "targets" by binding to complementary sequences in their 3' untranslated region. In this study, we examined the importance of the base-pairing strength of the miRNA-target duplex to repression. We hypothesized that if base-pairing strength affects the functionality of miRNA repression, organisms with higher body temperature or that live at higher temperatures will have miRNAs with higher G/C content so that the miRNA-target complex will remain stable. In the nine model organisms examined, we found a significant correlation between the average G/C content of miRNAs and physiological temperature, supporting our hypothesis. Next, for each organism examined, we compared the average G/C content of miRNAs that are conserved among distant organisms and that of miRNAs that are evolutionarily recent. We found that the average G/C content of ancient miRNAs is lower than recent miRNAs in homeotherms, whereas the trend was inversed in poikilotherms, suggesting that G/C content is associated with temperature, thus further supporting our hypothesis. In the organisms examined, the average G/C content of miRNA "seed" sequences was higher than that of mature miRNAs, which was higher than pre-miRNA loops, suggesting an association between the degree of functionality of the sequence and its average G/C content. Our analyses show a possible association between the base-pairing strength of miRNA-targets and the temperature of an organism, suggesting that base-pairing strength plays a role in repression by miRNAs.
微小 RNA（miRNAs）是短的单链 RNA，可以通过降解 mRNA 或抑制翻译来沉默基因表达。每个 miRNA 通过与 3'非翻译区中的互补序列结合来调节特定的 mRNA“靶标”集。在这项研究中，我们研究了 miRNA-靶标双链体的碱基配对强度对抑制作用的重要性。我们假设如果碱基配对强度影响 miRNA 抑制的功能，那么体温较高或生活在较高温度下的生物体将具有更高 G/C 含量的 miRNA，以使 miRNA-靶标复合物保持稳定。在检查的九个模式生物中，我们发现 miRNA 的平均 G/C 含量与生理温度之间存在显著相关性，支持了我们的假设。接下来，对于每个检查的生物体，我们比较了在远距离生物体中保守的 miRNA 和进化上较新的 miRNA 的平均 G/C 含量。我们发现，在恒温动物中，古老 miRNA 的平均 G/C 含量低于最近的 miRNA，而在变温动物中则相反，这表明 G/C 含量与温度有关，进一步支持了我们的假设。在所检查的生物体中，miRNA“种子”序列的平均 G/C 含量高于成熟 miRNA，而成熟 miRNA 的平均 G/C 含量高于 pre-miRNA 环，这表明序列的功能程度与其平均 G/C 含量之间存在关联。我们的分析表明 miRNA-靶标之间的碱基配对强度与生物体的温度之间可能存在关联，这表明碱基配对强度在 miRNA 抑制中发挥作用。
