Meerovitch K, Svitkin Y V, Lee H S, Lejbkowicz F, Kenan D J, Chan E K, Agol V I, Keene J D, Sonenberg N
Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
J Virol. 1993 Jul;67(7):3798-807. doi: 10.1128/JVI.67.7.3798-3807.1993.
Translation initiation on poliovirus RNA occurs by internal binding of ribosomes to a sequence within the 5' untranslated region. We have previously characterized a HeLa cell protein, p52, that binds to a fragment of the poliovirus 5' untranslated region (K. Meerovitch, J. Pelletier, and N. Sonenberg, Genes Dev. 3:1026-1034, 1989). Here we report the purification of the HeLa p52. Protein microsequencing identified p52 as La autoantigen. The La protein is a human antigen that is recognized by antibodies from patients with autoimmune disorders such as systemic lupus erythematosus and Sjögren's syndrome. We show that the La protein stimulates translation of poliovirus RNA, but not brome mosaic virus, tobacco mosaic virus, and alfalfa mosaic virus 4 RNA, translation in a reticulocyte lysate. In addition, La corrects aberrant translation of poliovirus RNA in a reticulocyte lysate. Subcellular immunolocalization showed that La protein is mainly nuclear, but after poliovirus infection, La is redistributed to the cytoplasm. Our results suggest that La protein is involved in poliovirus internal initiation of translation and might function through a similar mechanism in the translation of cellular mRNAs.
脊髓灰质炎病毒RNA的翻译起始是通过核糖体与5'非翻译区内的一个序列进行内部结合来实现的。我们之前鉴定了一种HeLa细胞蛋白p52，它能与脊髓灰质炎病毒5'非翻译区的一个片段结合（K. 梅罗维奇、J. 佩尔蒂埃和N. 索嫩贝格，《基因与发育》3:1026 - 1034，1989年）。在此我们报告HeLa细胞p52的纯化情况。蛋白质微量测序鉴定出p52为La自身抗原。La蛋白是一种人类抗原，可被自身免疫性疾病（如系统性红斑狼疮和干燥综合征）患者的抗体所识别。我们发现La蛋白能刺激脊髓灰质炎病毒RNA的翻译，但不能刺激网状细胞裂解物中雀麦花叶病毒、烟草花叶病毒和苜蓿花叶病毒4 RNA的翻译。此外，La能纠正网状细胞裂解物中脊髓灰质炎病毒RNA的异常翻译。亚细胞免疫定位显示，La蛋白主要位于细胞核中，但在脊髓灰质炎病毒感染后，La会重新分布到细胞质中。我们的结果表明，La蛋白参与了脊髓灰质炎病毒的内部翻译起始过程，并且可能在细胞mRNA的翻译中通过类似机制发挥作用。
