The mRNA cap epitranscriptome: Understanding an essential novel layer of gene expression in neuronal differentiation and function

mRNA 帽表观转录组：了解神经元分化和功能中基因表达的重要新层

基本信息

批准号：
BB/X008193/1
负责人：
Matthias Soller
金额：
$ 78.63万
依托单位：
University of Birmingham
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2023
资助国家：
英国
起止时间：
2023 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=BB%2FX008193%2F1
关键词：
mRNA cap epitranscriptome Understanding essential

项目摘要

The information for life is encoded in the DNA of the genes harboured in our chromosomes. The DNA in a chromosome is a very long chain consisting of four different nucleotides: G, A, C and T. For most genes this code is then converted into a messenger RNA intermediate (mRNA) that has a cap structure and a polyA tail to protect it from degradation. This mRNA is then translated in the cytoplasm into a chain of amino acids called proteins, which fulfil a function; for example an enzymatic reaction to generate energy from the nutrients we eat to allow for the electrical communication among neurons in our brain. Although the sequence of mRNA only consist of four nucleotides, many can be modified by addition of small chemical groups to increase the regulatory portfolio and coding capacity. The most prominent modification in mRNA are methyl groups added to the nucleotides adjacent to the cap structure. Animals including humans have two cap methyltransferase enzymes (CMTrs) that add these modifications. Also many parasites have a CMTr gene in their genome that is required for their propagation. In mice, CMTrs are essential and required for neuronal development, however, the biological functions of CMTrs and the mRNA cap modifications remain largely unexplained.We recently discovered that mutant Drosophila lacking both CMTrs are viable, although they suffer from neurological and learning defects. Intriguingly, we further discovered that in these mutant flies, mRNAs were not properly transported to synapses, which are the sites where signals are transmitted to neighbouring neurons. In particular, we could show that some mRNAs are only made into protein at synapses. Hence, the cap modifications have an essential role in directing the synthesis of new proteins locally at synapses suggesting that this process is required for learning of new associations, that are then stored as memory in the brain. However, we currently do not know which genes are expressed in this way at synapses nor what the sequence code is to direct mRNAs to synapses for localized expression.We now have the ideal animal model to address the very fundamental questions about how this enigmatic modifications direct local expression of genes to synapses. Our preliminary data indicate that the cap modifications vary between different animals and conditions. Since CMTrs also localize to synapses, our data suggest a dynamic code important for local protein synthesis. In a first step to crack this code, we will identify specific mRNAs that localize to synapses allowing us to build a reporter system to test the code. To complement this analysis we will further determine the sequence preferences of CMTrs in biochemical assays and identify proteins important for CMTr specificity and decoding of the cap modification code. These studies are essential to understand the vital function of the cap modifications in the regulation of gene expression and how its aberrant regulation can lead to neurological defects in humans, or can be exploited to interfere with viral replication such as in SARS-CoV-2.

生命的信息是在我们染色体中含有的基因的DNA中编码的。染色体中的DNA是一条非常长的链，由四个不同的核苷酸组成：G，A，C和T。对于大多数基因，此代码然后将其转换为具有盖结构和Polya尾巴的Messenger RNA中间体（mRNA），以保护其免受降解。然后将该mRNA在细胞质中翻译成一个称为蛋白质的氨基酸链，该氨基酸达到功能。例如，一种酶促反应从我们吃的营养中产生能量，以使大脑中的神经元之间进行电通信。尽管mRNA的序列仅由四个核苷酸组成，但可以通过添加小型化学基团来改变许多核苷酸，以增加调节作用组合和编码能力。 mRNA中最突出的修饰是将甲基添加到帽结构附近的核苷酸中。包括人在内的动物具有两个添加这些修饰的帽甲基转移酶（CMTR）。同样，许多寄生虫在其基因组中都有一个CMTR基因，这是其传播所必需的。在小鼠中，CMTR是神经元发育至关重要的，但是，CMTR的生物学功能和mRNA CAP修饰仍然在很大程度上无法解释。我们最近发现，尽管它们遭受神经学和学习缺陷的影响，但缺乏两种CMTR的突变果蝇都是可行的。有趣的是，我们进一步发现，在这些突变的苍蝇中，mRNA无法正确运输到突触，这些位点是信号传输到邻近神经元的位置。特别是，我们可以证明某些mRNA仅在突触时形成蛋白质。因此，盖帽修改在指导新蛋白质的合成在突触的本地合成中具有至关重要的作用，这表明该过程是学习新关联所必需的，然后将其存储为大脑中的记忆。但是，我们目前不知道以这种方式以这种方式表达哪些基因，也不知道序列代码指导mRNA的局部表达式突触是什么。我们现在有理想的动物模型来解决有关这种神秘修饰如何将基因局部表达的非常基本的问题引导到突触。我们的初步数据表明，不同动物和条件之间的帽帽修饰有所不同。由于CMTR也本地化为突触，因此我们的数据表明，动态代码对于局部蛋白质合成很重要。在破解此代码的第一步中，我们将确定特定的mRNA，这些mRNA本地化为突触，使我们能够构建一个记者系统来测试代码。为了补充该分析，我们将进一步确定CMTR在生化测定中的序列偏好，并确定对CMTR特异性和解码CAP修饰代码重要的蛋白质。这些研究对于理解基因表达调节中的帽修饰的重要功能以及其异常调节如何导致人类神经缺陷，或者可以利用以干扰病毒复制（例如在SARS-COV-2中）。