Kohn Andrea B, Sanford Rachel S, Yoshida Masa-aki, Moroz Leonid L
*The Whitney Laboratory for Marine Bioscience, University of Florida, 9505 Ocean Shore Blvd, St Augustine, FL 32080, USA;
*The Whitney Laboratory for Marine Bioscience, University of Florida, 9505 Ocean Shore Blvd, St Augustine, FL 32080, USA; Department of Neuroscience, University of Florida, Gainesville, FL 32611, USA;
Integr Comp Biol. 2015 Dec;55(6):1111-20. doi: 10.1093/icb/icv065. Epub 2015 Jun 18.
RNA editing is a process of targeted alterations of nucleotides in all types of RNA molecules (e.g., rRNA, tRNA, mRNA, and miRNA). As a result, the transcriptional output differs from its genomic DNA template. RNA editing can be defined both by biochemical mechanisms and by enzymes that perform these reactions. There are high levels of RNA editing detected in the mammalian nervous system, suggesting that nervous systems use this mechanism to increase protein diversity, because the post-transcription modifications lead to new gene products with novel functions. By re-annotating the ctenophore genomes, we found that the number of predicted RNA-editing enzymes is comparable to the numbers in mammals, but much greater than in other non-bilaterian basal metazoans. However, the overall molecular diversity of RNA-editing enzymes in ctenophores is lower, suggesting a possible "compensation" by an expansion of the ADAT1-like subfamily in this lineage. In two genera of ctenophores, Pleurobrachia and Mnemiopsis, there are high levels of expression for RNA-editing enzymes in their aboral organs, the integrative center involved in control of locomotion and geotaxis. This finding supports the hypothesis that RNA editing is correlated with the complexity of tissues and behaviors. Smaller numbers of RNA-editing enzymes in Porifera and Placozoa also correlates with the primary absence of neural and muscular systems in these lineages. In ctenophores, the expansion of the RNA-editing machinery can also provide mechanisms that support the remarkable capacity for regeneration in these animals. In summary, despite their compact genomes, a wide variety of epigenomic mechanisms employed by ctenophores and other non-bilaterian basal metazoans can provide novel insights into the evolutionary origins of biological novelties.
RNA编辑是对所有类型的RNA分子（如rRNA、tRNA、mRNA和miRNA）中的核苷酸进行靶向改变的过程。因此，转录产物与其基因组DNA模板不同。RNA编辑既可以通过生化机制来定义，也可以通过执行这些反应的酶来定义。在哺乳动物神经系统中检测到高水平的RNA编辑，这表明神经系统利用这种机制来增加蛋白质多样性，因为转录后修饰会产生具有新功能的新基因产物。通过重新注释栉水母基因组，我们发现预测的RNA编辑酶数量与哺乳动物中的数量相当，但远多于其他非两侧对称的基础后生动物。然而，栉水母中RNA编辑酶的整体分子多样性较低，这表明该谱系中ADAT1样亚家族的扩张可能起到了“补偿”作用。在栉水母的两个属——侧腕水母属和海月水母属中，RNA编辑酶在它们的反口器官（参与控制运动和地趋性的整合中心）中表达水平很高。这一发现支持了RNA编辑与组织和行为复杂性相关的假说。多孔动物门和扁盘动物门中RNA编辑酶数量较少，这也与这些谱系中主要缺乏神经和肌肉系统相关。在栉水母中，RNA编辑机制的扩张还可以提供支持这些动物显著再生能力的机制。总之，尽管栉水母和其他非两侧对称的基础后生动物的基因组紧凑，但它们所采用的多种表观基因组机制能够为生物新特性的进化起源提供新的见解。
