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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是eRF1与核糖体A位点结合所必需的。我们之前报道了一种 GTP 结合蛋白，其羧基端序列与真核延伸因子 EF1α 同源，与 eRF1 形成复合物，在翻译终止中充当 eRF3，并且 eRF3 由类似 EF1α 的羧基端 (C) 和氨基端 (N) 结构域组成。在本研究中，我们研究了eRF3及其相关G蛋白的结构和功能。本研究获得的主要发现总结如下：1)eRF3的C结构域与eRF1相关，而N结构域能够结合聚腺苷酸结合蛋白(PABP)，其与mRNA的聚(A)尾相关联，可能是为了稳定它们。 2)当eRF3-N结构域和PABP之间的相互作用被消除时，由于poly(A)尾缩短的抑制，所有mRNA的衰减率降低。 3)我们鉴定了一种被PABP激活的聚腺苷酸核酸酶(PAN)复合物，并发现eRF3和PAN复合物竞争性地结合PABP。这些结果表明翻译终止偶联的 mRNA 衰减是通过 eRF3 依赖性聚腺苷酸缩短介导的。因此，eRF3 不仅在翻译终止中充当 eRF1 载体蛋白，而且还充当 mRNA 降解机制的启动子。 4)我们还研究了与eRF3结构相关的其他G蛋白（Ski7和eRFS）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以调节mRNA稳定性。