A CYTOPLASMIC 57-KDA PROTEIN THAT IS REQUIRED FOR TRANSLATION OF PICORNAVIRUS RNA BY INTERNAL RIBOSOMAL ENTRY IS IDENTICAL TO THE NUCLEAR PYRIMIDINE TRACT-BINDING PROTEIN
A CYTOPLASMIC 57-KDA PROTEIN THAT IS REQUIRED FOR TRANSLATION OF PICORNAVIRUS RNA BY INTERNAL RIBOSOMAL ENTRY IS IDENTICAL TO THE NUCLEAR PYRIMIDINE TRACT-BINDING PROTEIN
复制标题
DOI：
10.1073/pnas.90.16.7642
复制
发表时间：
1993-08-15
影响因子：
11.1
通讯作者：
WIMMER, E
中科院分区：
文献类型：
--
作者：
HELLEN, CUT;WITHERELL, GW;WIMMER, E
小核糖核酸病毒如脊髓灰质炎病毒和脑心肌炎病毒的RNA基因组的翻译起始是帽非依赖性的，并且是核糖体与这些mRNA的5'非编码区的一段称为内部核糖体进入位点的相互作用的结果。遗传和生物化学研究表明，57 kDa的细胞质RNA结合蛋白（p57）在这种翻译机制中起着重要作用。我们现在已经发现，p57与嘧啶片段结合蛋白（PTB）具有相同的物理、生化和抗原特性，PTB是一种核蛋白，参与了涉及前mRNA的各种过程。这些数据表明p57和PTB是相同的蛋白。纯化的重组PTB特异性结合到脑心肌炎病毒的内部核糖体进入位点内的凸起发夹，并且对该发夹的突变衍生物和不相关的RNA具有低得多的亲和力。p57/PTB从HeLa无细胞裂解物的免疫耗竭抑制脊髓灰质炎病毒和脑心肌炎病毒mRNA的翻译，但对β-珠蛋白mRNA的翻译没有影响，证实了p57在翻译中通过内部核糖体进入的重要作用。
Initiation of translation of the RNA genomes of picornaviruses such as poliovirus and encephalomyocarditis virus is cap-independent and results from interaction of ribosomes with a segment of the 5' noncoding region of these mRNAs termed the internal ribosomal entry site. Genetic and biochemical studies have previously shown that a 57-kDa cytoplasmic RNA-binding protein (p57) plays an essential role in this translation mechanism. We have now found that p57 shares physical, biochemical, and antigenic properties with the pyrimidine tract-binding protein (PTB), a nuclear protein that has been implicated in various processes involving pre-mRNA. These data indicate that p57 and PTB are the same protein. Purified recombinant PTB bound specifically to a bulged hairpin within the internal ribosomal entry site of encephalomyocarditis virus and had a much lower affinity for a mutated derivative of this hairpin and for unrelated RNAs. Immunodepletion of p57/PTB from a HeLa cell-free lysate inhibited translation of poliovirus and encephalomyocarditis virus mRNAs but had no effect on translation of beta-globin mRNA, confirming the essential role of p57 in translation by internal ribosomal entry.