The role of non-AUG codons in translation initiation and localisation of mitochondrial proteins

非 AUG 密码子在线粒体蛋白翻译起始和定位中的作用

• 批准号: BB/L010097/1
• 负责人: Mark Coldwell
• 金额: $ 44.14万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FL010097%2F1
• 关键词: role; non; AUG; codons; translation

The DNA sequence in every cell of the body, termed the genome, stores the instructions to make all the proteins that are the essential building blocks needed for living. The code for each protein is stored in shorter stretches of DNA called genes. Converting the DNA sequence of a gene (which has only four "letters") to that of its corresponding protein (made up of twenty different kinds of amino acids) requires two major processes: transcription and translation. Transcription is the copying of the sequence information in the DNA into a similar molecule called messenger RNA (mRNA). The mRNA messages are then decoded into the amino acid sequence using the process of translation (so called because it goes from the language of DNA/RNA, to the language of amino acids). The "Genetic Code", which is used to translate nucleotides (RNA) into amino acids (protein), is well established and it is easy to predict what amino acids are encoded by a given stretch of DNA. The process is complicated, however, by the presence of "untranslated regions" at the ends of the mRNA, which do not encode any protein sequence. As a consequence, in order to correctly translate a protein, it is important to know where translation begins.The complex molecular machine that translates the mRNA sequence is called the ribosome, which starts making a protein when it finds a particular sequence in the mRNA called a translation initiation codon, which usually has the sequence "AUG". This project will advance our knowledge regarding the nature of these translation initiation codons. Many of the rules of translation initiation remain unclear therefore the more we know, the more we can understand from existing data. This is particularly true as improvements in sequencing technology means that an ever-increasing proportion of our knowledge about the protein universe is derived purely from applying these rules computationally to DNA sequence data.It is well established that multiple proteins can be produced from a single gene by generating different mRNA sequences during transcription. A much more recent finding is that translation can similarly produce different proteins from the same mRNA by the ribosome beginning to translate the protein at different positions, making longer or shorter versions of the protein. This project is concerned with how and why different translation initiation codons are used and how widespread this phenomenon is. So far, there are only a few examples where this has been discovered but those that are known are very important. In fact alternative initiation codons can be used to make new forms of proteins which have completely different functions or go to different places within the cell. Furthermore, it is now becoming clear that the initiation codon itself does not have to be the AUG triplet and the use of what we describe as non-canonical initiation codons is the focus of our proposed work.We have successfully identified translation initiation from non-AUG codons, and in this project we will particularly focus on genes that make proteins with roles in the "batteries" of the cell, the mitochondria. We believe that important signals within the proteins which help target them to this part of the cell have been ignored because they are made by starting from non-AUG codons. This means that computational methods using the wrong rules will have missed them. We have already proven this phenomenon in one gene, and once we have successfully identified novel initiation codons in further candidates, we will then examine what the consequences are for the proteins that are produced. We will certainly identify the signals that are involved in moving proteins to the mitochondria, but may also find new roles for the newly identified protein sequence.

身体每个细胞中的DNA序列，称为基因组，储存着制造所有蛋白质的指令，这些蛋白质是生活所需的基本组成部分。每种蛋白质的编码都存储在称为基因的较短DNA片段中。将一个基因的DNA序列（只有四个“字母”）转换成相应的蛋白质（由20种不同的氨基酸组成）需要两个主要过程：转录和翻译。转录是将DNA中的序列信息复制到称为信使RNA（mRNA）的类似分子中。然后，mRNA信息通过翻译过程被解码成氨基酸序列（之所以这么叫是因为它从DNA/RNA的语言变成了氨基酸的语言）。用于将核苷酸（RNA）翻译成氨基酸（蛋白质）的“遗传密码”已经很好地建立起来，并且很容易预测给定DNA片段编码的氨基酸。然而，由于mRNA末端存在不编码任何蛋白质序列的“非翻译区”，这一过程变得复杂。因此，为了正确翻译蛋白质，重要的是要知道翻译从哪里开始。翻译mRNA序列的复杂分子机器称为核糖体，当它在mRNA中找到称为翻译起始密码子的特定序列时，它开始制造蛋白质，通常具有序列“AUG”。这个项目将推进我们对这些翻译起始密码子的性质的认识。翻译起始的许多规则仍然不清楚，因此我们知道的越多，我们就越能从现有的数据中理解。随着测序技术的进步，我们对蛋白质宇宙的了解越来越多地来自于对DNA序列数据的计算，我们已经确定，通过在转录过程中产生不同的mRNA序列，可以从一个基因产生多种蛋白质。最近的一个发现是，翻译可以类似地从相同的mRNA产生不同的蛋白质，通过核糖体开始在不同的位置翻译蛋白质，从而产生更长或更短的蛋白质版本。这个项目关注的是如何和为什么使用不同的翻译起始密码子，以及这种现象有多普遍。到目前为止，只有少数几个例子已经被发现，但那些已知的是非常重要的。事实上，可以使用替代的起始密码子来制造新形式的蛋白质，这些蛋白质具有完全不同的功能或在细胞内的不同位置。此外，现在越来越清楚的是，起始密码子本身并不一定是AUG三联体，我们所描述的非典型起始密码子的使用是我们所提出的工作的重点。我们已经成功地从非AUG密码子中识别出翻译起始，在这个项目中，我们将特别关注制造蛋白质的基因，这些蛋白质在细胞的“电池”中发挥作用，线粒体。我们认为，蛋白质中帮助它们靶向细胞这一部分的重要信号被忽略了，因为它们是从非AUG密码子开始产生的。这意味着使用错误规则的计算方法将错过它们。我们已经在一个基因中证明了这一现象，一旦我们成功地在其他候选基因中识别出新的起始密码子，我们将研究产生的蛋白质的后果。我们肯定会确定参与将蛋白质移动到线粒体的信号，但也可能会发现新发现的蛋白质序列的新作用。

项目成果

G-quadruplexes mediate local translation in neurons.

G-四链体介导神经元中的局部翻译。

• DOI: 10.1042/bst20150053
• 发表时间: 2015
• 期刊: Biochemical Society transactions
• 影响因子: 3.9
• 作者: Schofield JP

A 5' UTR GGN repeat controls localisation and translation of a potassium leak channel mRNA through G-quadruplex formation.

• DOI: 10.1093/nar/gkaa699
• 发表时间: 2020-09-25
• 期刊: Nucleic acids research
• 影响因子: 14.9
• 作者: Maltby CJ;Schofield JPR;Houghton SD;O'Kelly I;Vargas-Caballero M;Deinhardt K;Coldwell MJ
• 通讯作者: Coldwell MJ