Bashkirov V I, Scherthan H, Solinger J A, Buerstedde J M, Heyer W D
Institute of General Microbiology, University of Bern, Switzerland.
J Cell Biol. 1997 Feb 24;136(4):761-73. doi: 10.1083/jcb.136.4.761.
Exoribonucleases are important enzymes for the turnover of cellular RNA species. We have isolated the first mammalian cDNA from mouse demonstrated to encode a 5'-3' exoribonuclease. The structural conservation of the predicted protein and complementation data in Saccharomyces cerevisiae suggest a role in cytoplasmic mRNA turnover and pre-rRNA processing similar to that of the major cytoplasmic exoribonuclease Xrn1p in yeast. Therefore, a key component of the mRNA decay system in S. cerevisiae has been conserved in evolution from yeasts to mammals. The purified mouse protein (mXRN1p) exhibited a novel substrate preference for G4 RNA tetraplex-containing substrates demonstrated in binding and hydrolysis experiments. mXRN1p is the first RNA turnover function that has been localized in the cytoplasm of mammalian cells. mXRN1p was distributed in small granules and was highly enriched in discrete, prominent foci. The specificity of mXRN1p suggests that RNAs containing G4 tetraplex structures may occur in vivo and may have a role in RNA turnover.
外切核糖核酸酶是参与细胞RNA种类周转的重要酶。我们从小鼠中分离出了首个被证明编码5'-3'外切核糖核酸酶的哺乳动物cDNA。预测蛋白质的结构保守性以及酿酒酵母中的互补数据表明，它在细胞质mRNA周转和前体rRNA加工中发挥的作用，类似于酵母中主要的细胞质外切核糖核酸酶Xrn1p。因此，从酵母到哺乳动物的进化过程中，酿酒酵母mRNA降解系统的一个关键组分得以保留。在结合和水解实验中，纯化的小鼠蛋白（mXRN1p）对含G4 RNA四链体的底物表现出一种新的底物偏好性。mXRN1p是首个被定位到哺乳动物细胞质中的RNA周转功能蛋白。mXRN1p分布于小颗粒中，并在离散的显著病灶中高度富集。mXRN1p的特异性表明，含G4四链体结构的RNA可能在体内存在，并可能在RNA周转中发挥作用。
