OVEREXPRESSION OF EUKARYOTIC PROTEIN-SYNTHESIS INITIATION FACTOR-4E IN HELA-CELLS RESULTS IN ABERRANT GROWTH AND MORPHOLOGY
OVEREXPRESSION OF EUKARYOTIC PROTEIN-SYNTHESIS INITIATION FACTOR-4E IN HELA-CELLS RESULTS IN ABERRANT GROWTH AND MORPHOLOGY
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DOI：
10.1073/pnas.87.21.8212
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发表时间：
1990-11-01
影响因子：
11.1
通讯作者：
RHOADS, RE
中科院分区：
文献类型：
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作者：
DEBENEDETTI, A;RHOADS, RE
真核蛋白合成起始因子4 E（eIF-4 E）是一种25 kDa的多肽，与mRNA的含7-甲基鸟苷帽结合，并参与mRNA向40 S核糖体亚基的转移，这是大多数细胞条件下蛋白质合成的限速步骤。eIF-4 E是丰度最低的起始因子，其存在浓度约为mRNA摩尔浓度的10%，因此可能作为mRNA募集到多聚核糖体中的调节位点。以前的研究表明，在Ser-53磷酸化的eIF-4 E与蛋白质合成的速度增加在体内的各种系统，并需要eIF-4 E成为结合到48 S起始复合物。在这项研究中，我们表明，eIF-4 E在HeLa细胞中使用附加型复制，BK病毒为基础的载体过表达导致一个不寻常的表型：细胞生长迅速，形成密集的，多层灶。它们逐渐形成合胞体，一些包含多达六个核，并最终在转染后1个月裂解。其中一些特性使人联想到致癌转化细胞。用表达eIF-4 E变体的相同载体转染的细胞正常生长，所述eIF-4 E变体在53位含有丙氨酸，因此不能在主要体内位点磷酸化。在同一载体中使用Ala-53变体或细菌氯霉素乙酰转移酶报告基因的估计表明，eIF-4 E过表达的程度是内源性水平的3至9倍。这些结果表明，eIF-4 E可能在细胞周期进程中发挥关键作用。
Eukaryotic protein synthesis initiation factor 4E (eIF-4E) is a 25-kDa polypeptide that binds to the 7-methylguanosine-containing cap of mRNA and participates in the transfer of mRNA to the 40S ribosomal subunit, a step that is rate-limiting for protein synthesis under most cellular conditions. eIF-4E is the least abundant of the initiation factors, is present at approximately 10% of molar concentration of mRNA, and thus may serve as a site of regulation for the recruitment of mRNA into polysomes. Previous studies have indicated that phosphorylation of eIF-4E at Ser-53 is correlated with an increased rate of protein synthesis in a variety of systems in vivo and is required for eIF-4E to become bound to the 48S initiation complex. In this study we show that overexpression of eIF-4E in HeLa cells using an episomally replicating, BK virus-based vector leads to an unusual phenotype: cells grow rapidly, forming densely packed, multilayered foci. They progressively form syncytia, some containing as many as six nuclei, and ultimately lyse 1 month after transfection. Some of these properties are reminiscent of oncogenically transformed cells. Cells transfected with the identical vector expressing a variant of eIF-4E, which contains alanine at position 53 and thus cannot be phosphorylated at the major in vivo site, grow normally. Estimations using the Ala-53 variant or a bacterial chloramphenicol acetyltransferase reporter gene in the same vector indicate that the degree of eIF-4E overexpression is 3- to 9-fold more than the endogenous level. These results suggest that eIF-4E may play a key role in cell cycle progression.