权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

The structure and function of a novel G protein family regulating eukaryotic mRNA dynamics

调节真核mRNA动态的新型G蛋白家族的结构和功能

基本信息

批准号：
13854025
负责人：
KATADA Toshiaki
金额：
$ 78.87万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (S)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2005
项目状态：
已结题

项目摘要

In eukaryotic protein synthesis, all three termination codons are directly recognized by a polypeptide-chain releasing factor, eRF1,to release polypeptide chain from ribosome, and another releasing factor, eRF3,is required for eRF1 binding to ribosomal A site. We previously reported that a GTP-binding protein, whose carboxy-terminal sequence is homologous to the eukaryotic elongation factor EF1α, forms a complex with eRF1 to function as eRF3 in the translation termination and that eRF3 consists of the EF1α-like carboxy-terminal (C) and amino-terminal (N) domains. In the present studies, we investigated the structures and functions of eRF3 and its related G proteins. The major findings obtained in this study are summarized as follows.1)The C domain of eRF3 associated with eRF1,whereas the N domain was capable of binding to poly-adenylate binding protein (PABP) associating with the poly(A) tail of mRNAs presumably for their stabilization. 2)When the interaction between eRF3-N domain and PABP was abolished, decay rate of all mRNAs was decreased due to the inhibition of poly(A) tail shortening. 3)We identified a poly(A) nuclease (PAN) complex that is activated by PABP and found that eRF3 and PAN complex competitively bound to PABP. These results indicate that the translation termination-coupled mRNA decay is mediated through eRF3-dependent poly(A) shortening. Thus, eRF3 functions not only as an eRF1-carrier protein in the translation termination but also as an initiator of the mRNA degradation machinery. 4)We also investigated the functions of other G proteins (Ski7 and eRFS) structurally related to eRF3 and found that the N domains of these G proteins commonly interact with factors involved in mRNA-degradation machineries to regulate mRNA stabilization.

在真核蛋白质合成中，所有三个终止密码子都被多肽链释放因子eRF1直接识别以从核糖体释放多肽链，而另一个释放因子eRF3则需要eRF1与核糖体A位点结合。我们先前报道，GTP结合蛋白的羧基末端序列与真核细胞延伸因子Ef1α同源，与eRF1形成复合体，在翻译终止中发挥eRF3的功能，eRF3由Ef1类α羧基末端(C)和氨基末端(N)组成。在本研究中，我们对eRF3及其相关G蛋白的结构和功能进行了研究。本研究的主要发现如下：1)eRF3的C结构域与eRF1结合，而N结构域能够与多聚腺苷结合蛋白(PABP)结合，与mRNAs的聚(A)尾巴结合，可能是为了稳定它们。2)当取消eRF3-N结构域与PABP的相互作用时，所有mRNAs的衰减率都降低，这是因为抑制了Poly(A)尾巴的缩短。3)我们鉴定了一个被PABP激活的聚(A)核酸酶(PAN)复合体，发现eRF3和PAN复合体与PABP竞争性结合。这些结果表明，翻译终止偶联的mRNA衰变是通过eRF3依赖的Poly(A)缩短所介导的。因此，eRF3不仅在翻译终止过程中作为eRF1载体蛋白发挥作用，而且还作为mRNA降解机制的启动者。4)我们还研究了结构上与eRF3相关的其他G蛋白(Ski7和ERF)的功能，发现这些G蛋白的N结构域通常与参与mRNA降解机制的因子相互作用来调节mRNA的稳定。