Identification and characterization of eukaryotic initiation factor 5A-2
Identification and characterization of eukaryotic initiation factor 5A-2
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DOI：
10.1046/j.1432-1033.2003.03806.x
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发表时间：
2003-11-01
期刊：
影响因子：
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通讯作者：
Johansson, HE
中科院分区：
文献类型：
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作者：
Clement, PMJ;Henderson, CA;Johansson, HE
系统发育保守的真核翻译起始因子5A（eIF5A）是已知的唯一含有翻译后衍生氨基酸hypusine [N-epsilon-（4-氨基-2-羟基丁基）赖氨酸]的细胞蛋白。eIF5A和它的假设模。阳离子是细胞持续增殖所必需的。正常情况下，只有一种eIF5A蛋白在人类细胞中表达。最近，我们发现了第二个人类EIF5A基因，该基因编码一个具有84%序列同一性的异构体（EIF5A -2）。eIF5A-2 mRNA在某些人类癌细胞中过表达，与仅限于人类睾丸和大脑的弱正常表达相反，表明EIF5A2是一种潜在的致癌基因。然而，迄今为止还没有在人类或哺乳动物细胞中描述过eIF5A-2蛋白。在这里，我们描述了在过表达eIF5A-2 mrna的人类结直肠癌和卵巢癌细胞系SW-480和UACC-1598中eIF5A-2蛋白的鉴定。人类同种异构体的功能表征表明，人类EIF5A基因可以补充酵母EIF5A基因被破坏的酵母菌株的生长。这表明eIF5A-2在酵母菌中与人类同种异构体的功能相似，并表明eIF5A-2在真核细胞存活中具有重要作用，类似于无处不在的eIF5A-1。可检测的结构差异也被注意到，包括缺乏免疫交叉反应性，与脱氧hypusine合成酶形成不同的复合物，以及K-m值（分别为1.5 +/- 0.2和8.3 +/- 1.4 muM）作为脱氧hypusine合成酶的底物。这些物理特征和C末端不同的氨基酸序列以及基因表达模式的差异暗示了eIF5A-2亚型在哺乳动物和癌症中具有分化的、组织特异性的功能。
The phylogenetically conserved eukaryotic translation initiation factor 5A(eIF5A) is the only known cellular protein to contain the post-translationally derived amino acid hypusine [N-epsilon-(4-amino-2-hydroxybutyl)lysine]. Both eIF5A and its hypusine modi. cation are essential for sustained cell proliferation. Normally only one eIF5A protein is expressed in human cells. Recently, we identified a second human EIF5A gene that would encode an isoform (eIF5A-2) of 84% sequence identity. Overexpression of eIF5A-2 mRNA in certain human cancer cells, in contrast to weak normal expression limited to human testis and brain, suggests EIF5A2 as a potential oncogene. However, eIF5A-2 protein has not been described in human or mammalian cells heretofore. Here, we describe the identification of eIF5A-2 protein in human colorectal and ovarian cancer lines, SW-480 and UACC-1598, that overexpress eIF5A-2 mRNAs. Functional characterization of the human isoforms revealed that either human EIF5A gene can complement growth of a yeast strain in which the yeast EIF5A genes were disrupted. This indicates functional similarity of the human isoforms in yeast and suggests that eIF5A-2 has an important role in eukaryotic cell survival similar to that of the ubiquitous eIF5A-1. Detectable structural differences were also noted, including lack of immunological cross-reactivity, formation of different complexes with deoxyhypusine synthase, and K-m values (1.5 +/- 0.2 vs. 8.3 +/- 1.4 muM for eIF5A-1 and -2, respectively) as substrates for deoxyhypusine synthase in vitro. These physical characteristics and distinct amino acid sequences in the C- terminal domain together with differences in gene expression patterns imply differentiated, tissue-specific functions of the eIF5A-2 isoform in the mammalian organism and in cancer.