unr, a cellular cytoplasmic RNA-binding protein with five cold-shock domains, is required for internal initiation of translation of human rhinovirus RNA
unr, a cellular cytoplasmic RNA-binding protein with five cold-shock domains, is required for internal initiation of translation of human rhinovirus RNA
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DOI：
10.1101/gad.13.4.437
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发表时间：
1999-02-15
影响因子：
10.5
通讯作者：
Jackson, RJ
中科院分区：
文献类型：
--
作者：
Hunt, SL;Hsuan, JJ;Jackson, RJ
动物小核糖核酸病毒RNA的翻译起始通过直接核糖体进入机制发生，其需要RNA的5' UTR的区段，称为内部核糖体进入位点（IRES）。此外，肠病毒和鼻病毒（HRV）亚组的翻译需要细胞反式作用因子，这些因子在兔网织红细胞中不存在或限制，但在HeLa细胞提取物中更丰富。先前已经表明，HeLa细胞含有两种可分离的活性，当用于补充网织红细胞裂解物时，每种活性独立地刺激HRV IRES依赖性翻译;其中一种活性被鉴定为聚嘧啶片段结合蛋白（PTB）。在此，通过使用基于HRV 5' UTR的RNA亲和柱实现第二活性的纯化。它包括两个组成部分：一个38-kD蛋白（p38），它是GH-WD重复蛋白家族的新成员，没有内在的RNA结合活性;和一个96-至97-kD蛋白双联体，它被鉴定为unr，一个具有五个冷休克结构域的RNA结合蛋白。与针对任一蛋白质的抗体的免疫共沉淀显示这两种蛋白质彼此相互作用，因此p38被命名为unrip（unr相互作用蛋白）。重组unr与重组PTB协同作用以刺激依赖于鼻病毒IRES的翻译。与此相反，unr没有显着增加脊髓灰质炎病毒IRES活性的PTB依赖性刺激。
Initiation of translation of the animal picornavirus RNAs occurs via a mechanism of direct ribosome entry, which requires a segment of the 5' UTR of the RNA, known as the internal ribosome entry site (IRES). In addition, translation of the enterovirus and rhinovirus (HRV) subgroups requires cellular trans-acting factors that are absent from, or limiting in rabbit reticulocytes, but are more abundant in HeLa cell extracts. It has been shown previously that HeLa cells contain two separable activities, each of which independently stimulates HRV IRES-dependent translation when used to supplement reticulocyte lysate; one of these activities was identified as polypyrimidine tract-binding protein (PTB). Here, the purification of the second activity is achieved by use of an RNA-affinity column based on the HRV 5' UTR. It comprises two components: a 38-kD protein (p38), which is a novel member of the GH-WD repeat protein family and has no intrinsic RNA-binding activity; and a 96- to 97-kD protein doublet, which was identified as unr, an RNA-binding protein with five cold-shock domains. Coimmunoprecipitation with antibodies against either protein shows that the two proteins interact with each other, and thus p38 is named unrip (unr-interacting protein). Recombinant unr acts synergistically with recombinant PTB to stimulate translation dependent on the rhinovirus IRES. In contrast, unr did not significantly augment the PTB-dependent stimulation of poliovirus IRES activity.