Human cell growth requires a functional cytoplasmic exosome, which is involved in various mRNA decay pathways
Human cell growth requires a functional cytoplasmic exosome, which is involved in various mRNA decay pathways
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DOI：
10.1261/rna.575107
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发表时间：
2007-07-01
期刊：
影响因子：
4.5
通讯作者：
Pruijn, Ger J. M.
中科院分区：
文献类型：
--
作者：
Van Dijk, Erwin L.;Schilders, Geurt;Pruijn, Ger J. M.
人外泌体是一种3 '-5'核糖核酸外切酶复合物，其在细胞核和细胞质中发挥作用以降解或加工RNA。关于这些不同细胞区室中的核心外泌体复合物之间的潜在差异以及单个亚基在维持稳定和功能复合物中的作用知之甚少。甘油梯度沉降分析表明，核外泌体的重要子集存在于比细胞质外泌体（类似于10 S）大得多的复合物（60- 80 S）中。有趣的是，siRNA介导的敲低实验表明，细胞质外泌体比核外泌体更有效地下调。此外，我们观察到hRrp 41 p或hRrp 4p的敲低而不是PM/ Scl-100或PM/ Scl-75的敲低导致其他亚基的编码。然而，需要PM/ Scl-100和PM/ Scl- 75来维持三种不同mRNA报告基因的正常水平：野生型β-珠蛋白mRNA、含有富含Au（ARE）不稳定元件的B-珠蛋白mRNA和带有提前终止密码子（PTC）的B-珠蛋白mRNA.在下调不同外泌体亚基（特别是PM/ Scl- 100）时，含有ARE和PTC的mRNA的水平增加似乎是由于周转率降低。这些结果表明，尽管外泌体稳定性不需要PM/ Scl-100和PM/ Scl-75，但它们作为功能性外泌体复合物的必需亚基或作为外泌体非依赖性蛋白参与mRNA降解。
The human exosome is a 3'-5' exoribonuclease complex that functions both in the nucleus and in the cytoplasm to either degrade or process RNA. Little is known yet about potential differences among core exosome complexes in these different cellular compartments and the roles of the individual subunits in maintaining a stable and functional complex. Glycerol gradient sedimentation analyses indicated that a significant subset of nuclear exosomes is present in much larger complexes (60-80S) than the cytoplasmic exosomes (similar to 10S). Interestingly, siRNA-mediated knock- down experiments indicated that the cytoplasmic exosome is down- regulated much more efficiently than the nuclear exosome. In addition, we observed that knockdown of hRrp41p or hRrp4p but not PM/ Scl-100 or PM/ Scl-75 leads to codepletion of other subunits. Nevertheless, PM/ Scl-100 and PM/ Scl- 75 are required to maintain normal levels of three different mRNA reporters: a wild- type beta-globin mRNA, a b- globin mRNA containing an AU- rich ( ARE) instability element, and a b- globin mRNA bearing a premature termination codon ( PTC). The increased levels of ARE- and the PTC-containing mRNAs upon down- regulation of the different exosome subunits, in particular PM/ Scl- 100, appeared to be due to decreased turnover rates. These results indicate that, although not required for exosome stability, PM/ Scl-100 and PM/ Scl-75 are involved in mRNA degradation, either as essential subunits of a functional exosome complex or as exosome- independent proteins.