Deciphering the role of 2’-O-methylated nucleosides in transposon control and neuronal function

人类基因组的近一半由转座元件(TE)组成，这些转座元件是重复的DNA元件，具有随着时间的推移动员和改变位置的能力。TE曾被认为是“垃圾”或“自私”的DNA，现在因其在各种生理过程中的功能作用而受到重视，这些作用可能对生物体有益，但也可能在不受控制的动员时变得病态。越来越多的证据出现在老年脑细胞TE动员增加和神经疾病之间。表观遗传机制，如DNA甲基化，和小的非编码RNA被认为在限制TE活性方面发挥着关键作用。RNA修饰的改变也与大脑疾病有关，但其潜在的分子机制目前尚不清楚。我们的初步数据表明，丰富的RNA修饰2‘-O-甲基化核苷(Nm)阻止了果蝇TE的动员，并导致神经元缺陷，表明RNA修饰、转座子控制和脑功能之间存在联系。本课题的目的是研究Nm在果蝇TE调控中的作用机制。更确切地说，我们将研究Nm甲基转移酶(MTS)在TE调节中的作用。具体的工作包包括：i)使用特定的遗传传感器以及基因组方法来分析受这些MT耗尽影响的TE和小RNA群体；ii)通过互补的高通量方法识别直接靶标；以及iii)这种RNA修饰与小RNA途径相互作用的分子和生化特征。近年来，RNA修饰的新领域，现在被称为表观转录，已经取得了重大进展，进入了基因表达调控的中心阶段。这项建议的研究有可能阐明它们在保护基因组免受转座子不受控制的动员以及在大脑疾病的病因学中所起作用的一个尚未探索的领域。鉴于MTS是众所周知的药物靶向性酶，该项目还应该为设计潜在的治疗应用开辟新的途径。

Almost half of the human genome is comprised of transposable elements (TE), which are repeat DNA elements that have the ability to mobilize and change locations over time. Once considered “junk” or “selfish” DNA, TE are now being appreciated for their functional roles in a variety of physiological processes, which can be beneficial to the organisms but can also become pathological upon uncontrolled mobilization. Mounting evidence is emerging between increased TE mobilization in aged brain cells and neurological disorders. Epigenetic mechanisms, such as DNA methylation, and small non-coding RNAs are known to play a crucial role to limit TE activity. Alterations of RNA modifications have also been linked to brain disorders but the underlying molecular mechanisms are currently unknown. Our preliminary data indicate that the abundant RNA modification 2’-O-methylated nucleosides (Nm) prevents TE mobilization in Drosophila melanogaster and that its alterations lead to neuronal defects, suggesting a link between RNA modifications, transposon control and brain function. The objective of this project is to investigate the mechanisms of Nm in the control of TE regulation in Drosophila. More precisely, we will study the function of Nm methyltransferases (MTs) in TE regulation. The specific work package includes: i) the use of specific genetic sensors as well as genomic approaches to analyze the population of TE and small RNAs that are affected upon depletion of these MTs; ii) the identification of direct targets by complementary high throughput approaches and iii) the molecular and biochemical characterization of the interplay of this RNA modification with small RNA pathways.The new field of RNA modifications, now termed Epitranscriptomics, has made major strides to the central stage of gene expression control in the recent years. The suggested study has the potential to illuminate a yet unexplored area of their role in protecting the genome against uncontrolled mobilization of transposons and in the etiology of brain disorders. Given that MTs are well known drug-targetable enzymes this project should also open new avenues to design potential therapeutic applications.