RNA chaperone activity of protein components of human Ro RNPs
RNA chaperone activity of protein components of human Ro RNPs
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DOI：
10.1261/rna.7263905
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发表时间：
2005-07-01
期刊：
影响因子：
4.5
通讯作者：
Steiner, G
中科院分区：
文献类型：
--
作者：
Belisova, A;Semrad, K;Steiner, G
Ro核糖核蛋白（RNP）复合物由一个小的非编码细胞质RNA分子（称为Y RNA）和两个蛋白质Ro60和La组成。其他蛋白质如hnRNP 1、hnRNP K或核蛋白最近被证明与Y rna亚群有关。Ro RNPs似乎定位于所有高等真核细胞的细胞质中，但其功能仍然难以捉摸。为了阐明Ro RNPs的可能功能，我们使用两种体外伴侣检测和另外一种体内伴侣检测来测试这些复合物的蛋白质成分的RNA伴侣特性。在这些分析中，测量了I族内含子的剪接活性。La在体外和体内顺式剪接实验中显示出明显的RNA伴侣活性，而在体外反式剪接实验中没有发现活性。hnRNP I和hnRNP K在两种体外实验中均表现出较强的伴侣活性，但在体内实验中被证明具有细胞毒性。体外未观察到Ro60的伴侣活性，体内检测到中等活性。La和hnRNP I的体外伴侣活性在与Y RNA结合后被完全抑制。综上所述，这些数据表明，Ro RNP组分La、hnRNP K和hnRNP I具有RNA伴侣活性，而Ro60-Y RNA复合物可能具有转运蛋白的功能，将其他Y RNA结合蛋白带到它们的特定靶点。
Ro ribonucleoprotein (RNP) complexes are composed of one molecule of a small noncoding cytoplasmic RNA, termed Y RNA, and the two proteins Ro60 and La. Additional proteins such as hnRNP 1, hnRNP K, or nucleolin have recently been shown to be associated with subpopulations of Y RNAs. Ro RNPs appear to be localized in the cytoplasm of all higher eukaryotic cells but their functions have remained elusive. To shed light on possible functions of Ro RNPs, we tested protein components of these complexes for RNA chaperone properties employing two in vitro chaperone assays and additionally an in vivo chaperone assay. In these assays the splicing activity of a group I intron is measured. La showed pronounced RNA chaperone activity in the cis-splicing assay in vitro and also in vivo, whereas no activity was seen in the trans-splicing assay in vitro. Both hnRNP I and hnRNP K exhibited strong chaperone activity in the two in vitro assays, however, proved to be cytotoxic in the in vivo assay. No chaperone activity was observed for Ro60 in vitro and a moderate activity was detected in vivo. In vitro chaperone activities of La and hnRNP I were completely inhibited upon binding of Y RNA. Taken together, these data suggest that the Ro RNP components La, hnRNP K, and hnRNP I possess RNA chaperone activity, while Ro60-Y RNA complexes might function as transporters, bringing other Y RNA binding proteins to their specific targets.