Assembly of AUF1 with eIF4G-poly(A) binding protein complex suggests a translation function in AU-rich mRNA decay
Assembly of AUF1 with eIF4G-poly(A) binding protein complex suggests a translation function in AU-rich mRNA decay
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DOI：
10.1261/rna.2308106
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发表时间：
2006-05-01
期刊：
影响因子：
4.5
通讯作者：
Schneider, RJ
中科院分区：
文献类型：
--
作者：
Lu, JY;Bergman, N;Schneider, RJ
位于许多短寿命mRNAs的3‘-非翻译区的富AU元素(ARE)是这些转录本的不稳定决定因素。AUF1/hnRNP D是一个ARE结合蛋白家族，由四种异构体组成，促进ARE-mRNAs的快速衰退。AUF1促进ARE-mRNA快速衰退的机制尚不清楚。AUF1已被证明在细胞中与帽起始复合体、热休克蛋白Hsp70和Hsc70以及其他未知因素形成RNase抗性复合体。为了了解AUF1复合体的功能，我们用生化方法研究了AUF1与翻译起始复合体的成分之间的关联。我们使用纯化的重组蛋白和人工合成的ARE RNA寡核苷酸来确定蛋白质在体外相互作用的层次以及AUF1与ARE结合对蛋白质复合体形成的影响。我们证明了所有四种AUF1蛋白亚型都在C-末端与启动因子eIF4G直接和强烈结合，而与AUF1与ARE的相互作用无关。AUF1被证明直接与聚(A)结合蛋白(PABP)相互作用，既不依赖eIF4G，也与eIF4G形成复合体。AUF1与ARE或Hsp70热休克蛋白的结合与AUF1-PABP的相互作用相反。在体内，AUF1与PABP的相互作用不会改变PABP的稳定性。在这些和其他数据的基础上，我们提出了一个AUF1的分子相互作用模型，该模型涉及AUF1-PABP复合体从ARE-mRNA中平移相关的位移，并可能揭开Poly(A)的尾巴。
An AU-rich element (ARE) located in the 3'-untranslated region of many short-lived mRNAs functions as an instability determinant for these transcripts. AUF1/hnRNP D, an ARE-binding protein family consisting of four isoforms, promotes rapid decay of ARE-mRNAs. The mechanism by which AUF1 promotes rapid decay of ARE-mRNA is unclear. AUF1 has been shown to form an RNase-resistant complex in cells with the cap-initiation complex and heat shock proteins Hsp70 and Hsc70, as well as other unidentified factors. To understand the function of the AUF1 complex, we have biochemically investigated the association of AUF1 with the components of the translation initiation complex. We used purified recombinant proteins and a synthetic ARE RNA oligonucleotide to determine the hierarchy of protein interactions in vitro and the effect of AUF1 binding to the ARE on the formation of protein complexes. We demonstrate that all four AUF1 protein isoforms bind directly and strongly to initiation factor eIF4G at a C-terminal site regardless of AUF1 interaction with the ARE. AUF1 is shown to directly interact with poly( A) binding protein ( PABP), both independently of eIF4G and in a complex with eIF4G. AUF1-PABP interaction is opposed by AUF1 binding to the ARE or Hsp70 heat shock protein. In vivo, AUF1 interaction with PABP does not alter PABP stability. Based on these and other data, we propose a model for the molecular interactions of AUF1 that involves translation-dependent displacement of AUF1-PABP complexes from ARE-mRNAs with possible unmasking of the poly(A) tail.