Levels and functions of non-canonical nucleosides in messenger RNA

作用于核苷酸的可逆修饰化学的发现是一个突破性的发现，并在此过程中导致了表观遗传研究出版物的淘金热。特别是，当人们发现信使RNA的化学成分可能比最初认为的更多样化时，RNA重新成为焦点。在这方面最突出的是腺苷修饰m6A。一旦被引入mRNA，它通过与特定的阅读器蛋白相互作用来提供越来越多的功能。我们最近发表了一项蛋白质组学研究，揭示了全新的连接，不仅通过吸引阅读蛋白，而且通过排斥它们来影响疾病相关途径。在这个过程中，许多其他的核苷酸修饰在mRNA和DNA中被发现。例如，m1A存在于mRNA中，而m6A存在于许多高等生物的DNA中，如藻类、昆虫、蠕虫甚至哺乳动物。然而，一些最初的发现必须加以改进。因此，发现m1A和m5C在mRNA中的丰度远低于最初假设的丰度。最初被描述为靶向m6A的去甲基化双加氧酶FTO最近被发现主要接受m6Am，就像在帽结构中发现的那样。此外，我们可以用高灵敏度的质谱法证明，m6dA可能不是哺乳动物DNA的天然成分。我们将继续努力验证mRNA中修饰碱基的存在。来自我们小组和最近出版物的详细数据显示，m62A和ms2i6A分别仅存在于rRNA和线粒体RNA中。然而，mRNA中部分高度修饰的核苷的存在仍然是研究的主要目标。因此，我们计划对mRNA中的核苷修饰进行深入调查。我们建议更详细地研究假尿苷和5'帽结构。我们将揭示它们的蛋白质相互作用组，并解开这些相互作用介导的功能机制。这些结果将有助于我们理解化学修饰对mRNA和基本细胞过程（如翻译成蛋白质）的相互作用。

The discovery of reversible modification chemistry acting on nucleotides was a breakthrough discovery and led in the course to a gold rush of publications in epigenetic research. In particular, RNA moved back into focus, when it was discovered that messenger RNA may be more chemically diverse than originally believed. Most prominent is the adenosine modification m6A in this respect. Once introduced into mRNA, it serves an ever growing number of functions by interacting with specific reader proteins. We recently published a proteomic study that reveled completely novel connections, influencing disease relevant pathways not only by attraction of reader proteins, but also by repelling them. In the course of the rush, many other nucleotide modifications were identified in mRNA and also DNA. For example, m1A was found in mRNA and the base m6A in the DNA of a number of higher organisms, like algae, insects, worms and even mammals. Some initial discoveries however, had to be refined. As such it was found that both m1A and m5C are far less abundant in mRNA than originally postulated. The demethylating dioxygenase FTO, which was initially described as targeting m6A was recently found to accept predominantly m6Am like it is found in the cap structure. In addition, we could demonstrate with highly sensitive mass spectrometry that m6dA may not be a native component of mammalian DNA as frequently postulated. We will continue our efforts to verify the occurrence of modified bases in mRNA. Detailed data from our group and recent publications revealed that m62A and ms2i6A are found exclusively in rRNA and mitochondrial RNA, respectively. Nevertheless, the presence of in part highly modified nucleosides in mRNA remains a prime target of research. Therefore we are planning to perform a deep survey of nucleoside modifications in mRNA. We propose to study particularly pseudouridine and the 5’ cap structure in more detail. We will reveal their protein-interactome and unravel the functional mechanisms mediated by these interactions. The results will help us to understand the interplay of chemical modification on mRNA and essential cellular processes like translation into proteins.