编辑推荐：
生物通报道，美国NIH以及Johns Hopkins医学院的研究者在蛋白延伸因子方面的研究取得新的进展，为蛋白翻译延伸因子调节蛋白翻译的研究打开了新的视野，文章标题Hypusine-containing protein eIF5A promotes translation elongation。
生物通报道，美国NIH以及Johns Hopkins医学院的研究者在蛋白延伸因子方面的研究取得新的进展，为蛋白翻译延伸因子调节蛋白翻译的研究打开了新的视野，文章标题Hypusine-containing protein eIF5A promotes translation elongation。
蛋白质合成分三个阶段：起始、延伸、终止，分别由不同的起始因子、延伸因子和终止因子（释放因子）参与。参与延伸的是延伸因子，它与核糖体结合促进蛋白合成。先前的研究发现了两种普遍的延伸因子，EF-Tu（在细菌中常见，与之相对应的在真核细胞中的叫eEF1A），和EF-G（eEF2）。它们功能分别是传递酰基-tRNA到核糖体上，促进核糖体异构。
现在，研究者们发现在酿酒酵母中，一个曾经认为是翻译启动子的因子eIF5A，其实是一个在延伸翻译过程中起核心作用的因子。
eIF5A它含有一个罕见的氨基酸，即Hypusine，Hypusine是确保eIF5A促进蛋白翻译延伸的关键。如果缺失掉酵母细胞内中的eIF5A，会导致蛋白翻译延伸缺陷，研究人员认为这个因子可能与eEF2一起发挥促进核糖体异构的作用。
（生物通 小茜）
生物通推荐原文检索：Hypusine-containing protein eIF5A promotes translation elongation
Preeti Saini1, Daniel E. Eyler2, Rachel Green2 & Thomas E. Dever1
Laboratory of Gene Regulation and Development, NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA
Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
【Abstract】
Top of pageTranslation elongation factors facilitate protein synthesis by the ribosome. Previous studies identified two universally conserved translation elongation factors, EF-Tu in bacteria (known as eEF1A in eukaryotes) and EF-G (eEF2), which deliver aminoacyl-tRNAs to the ribosome and promote ribosomal translocation, respectively1. The factor eIF5A (encoded by HYP2 and ANB1 in Saccharomyces cerevisiae), the sole protein in eukaryotes and archaea to contain the unusual amino acid hypusine (N -(4-amino-2-hydroxybutyl)lysine)2, was originally identified based on its ability to stimulate the yield (endpoint) of methionyl-puromycin synthesis—a model assay for first peptide bond synthesis thought to report on certain aspects of translation initiation3, 4. Hypusine is required for eIF5A to associate with ribosomes5, 6 and to stimulate methionyl-puromycin synthesis7. Because eIF5A did not stimulate earlier steps of translation initiation8, and depletion of eIF5A in yeast only modestly impaired protein synthesis9, it was proposed that eIF5A function was limited to stimulating synthesis of the first peptide bond or that eIF5A functioned on only a subset of cellular messenger RNAs. However, the precise cellular role of eIF5A is unknown, and the protein has also been linked to mRNA decay, including the nonsense-mediated mRNA decay pathway10, 11, and to nucleocytoplasmic transport12, 13. Here we use molecular genetic and biochemical studies to show that eIF5A promotes translation elongation. Depletion or inactivation of eIF5A in the yeast S. cerevisiae resulted in the accumulation of polysomes and an increase in ribosomal transit times. Addition of recombinant eIF5A from yeast, but not a derivative lacking hypusine, enhanced the rate of tripeptide synthesis in vitro. Moreover, inactivation of eIF5A mimicked the effects of the eEF2 inhibitor sordarin, indicating that eIF5A might function together with eEF2 to promote ribosomal translocation. Because eIF5A is a structural homologue of the bacterial protein EF-P14, 15, we propose that eIF5A/EF-P is a universally conserved translation elongation factor.
