The interaction of the cap-binding complex (CBC) with eIF4G is dispensable for translation in yeast
The interaction of the cap-binding complex (CBC) with eIF4G is dispensable for translation in yeast
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DOI：
10.1261/rna.5100903
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发表时间：
2003-06-01
期刊：
影响因子：
4.5
通讯作者：
Hentze, MW
中科院分区：
文献类型：
--
作者：
Baron-Benhamou, J;Fortes, P;Hentze, MW
在真核生物中，m(7)GpppN帽结构被添加到所有新生RNA聚合酶11转录本中，并在RNA代谢的多个步骤中发挥重要作用。在RNA合成过程中，以核为主的帽结合复合体（CBC）与帽结合。主要的细胞质真核起始因子4F （eIF4F）被认为在成熟mRNA输出到细胞质后取代CBC，并介导大部分细胞翻译。酵母和哺乳动物CBC在体外与eif4f的一个亚基eIF4G相互作用，在这项工作中，我们研究了这种相互作用在酵母翻译过程中的潜在作用。我们在酵母eIF4G的两个同工异构体之一的Tif4631p中发现了一个突变（DR548/9AA），该突变消除了其与CBC的结合。表达该突变蛋白作为eIF4G唯一来源的细胞以野生型速度生长，并且通过代谢标记和多体谱分析评估，大量细胞翻译没有变化。重要的是，我们发现DR548/9AA突变既不减少也不延迟新诱导的报告基因mRNA的翻译。最后，微阵列分析揭示了CBC亚基缺失菌株中显著的转录组改变，而eIF4G点突变体基本上具有野生型转录组组成。总的来说，这些数据表明，在酵母中，CBC缺失的表型后果与其与eIF4G的相互作用是可分离的，并且CBC-eIF4G的相互作用对于酵母中潜在的“先锋轮”翻译是必不可少的。
In eukaryotes, the m(7)GpppN cap structure is added to all nascent RNA polymerase 11 transcripts, and serves important functions at multiple steps of RNA metabolism. The predominantly nuclear cap-binding complex (CBC) binds to the cap during RNA synthesis. The predominantly cytoplasmic eukaryotic initiation factor 4F (eIF4F) is thought to replace CBC after export of mature mRNA to the cytoplasm, and mediates the bulk of cellular translation. Yeast as well as mammalian CBC interacts in vitro with eIF4G, a subunit of eIF4F. in this work, we investigate a potential role of this interaction during translation in yeast. We identify a mutation (DR548/9AA) in Tif4631p, one of two isoforms of yeast eIF4G, that abolishes its binding to CBC. Cells expressing this mutant protein as the sole source of eIF4G grow at wild-type rates, and bulk cellular translation, as assessed by metabolic labeling and polysome profile analysis, is unchanged. Importantly, we find that the DR548/9AA mutation neither diminishes nor delays the translation of newly induced reporter mRNA. Finally, microarray analysis reveals marked transcriptome alterations in CBC subunit deletion strains, whereas eIF4G point mutants have essentially a wild-type transcriptome composition. Collectively, these data suggest that in yeast, the phenotypic consequences of CBC deletions are separable from its interaction with eIF4G, and that the CBC-eIF4G interaction is dispensable for a potential "pioneering round" of translation in yeast.