The shuttling SR protein 9G8 plays a role in translation of unspliced mRNA containing a constitutive transport element
The shuttling SR protein 9G8 plays a role in translation of unspliced mRNA containing a constitutive transport element
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DOI：
10.1074/jbc.m701660200
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发表时间：
2007-07-06
影响因子：
4.8
通讯作者：
Hammarskjold, Marie-Louise
中科院分区：
文献类型：
--
作者：
Swartz, Jennifer E.;Bor, Yeou-Cherng;Hammarskjold, Marie-Louise
最近，剪接调控SR蛋白9G8被认为与输出蛋白Tap/Nxf1一起在mRNA输出中发挥作用。TAP与梅森-辉瑞猴子病毒构成运输元件(CTE)直接相互作用，CTE是一种能够输出含有内含子的未剪接的mRNA的元件。基于我们先前的发现，Tap可以促进CTE-RNA的多聚体结合和翻译，我们研究了9G8对细胞质RNA命运的影响。9G8可增强含有Mason-Pfizer猴病毒-CTE或新近发现的Tap-CTE的未剪接RNA的表达。9G8还增强了含有CTE的未剪接RNA的多聚核糖体结合。高磷酸化的9G8存在于单糖体和小的多聚核糖体中，而可溶性组分只含有低磷酸化的蛋白。我们的结果与一个模型是一致的，在该模型中，低磷酸化的SR蛋白在出口过程中保持稳定地与信使核糖核蛋白(MRNP)复合体结合，并在翻译启动过程中随着磷酸化的增加而释放。这些结果为RNA剪接、输出和翻译之间的关键联系提供了进一步的证据。
The splicing regulatory SR protein, 9G8, has recently been proposed to function in mRNA export in conjunction with the export protein, Tap/NXF1. Tap interacts directly with the Mason-Pfizer monkey virus constitutive transport element (CTE), an element that enables export of unspliced, intron-containing mRNA. Based on our previous finding that Tap can promote polysome association and translation of CTE-RNA, we investigated the effect of 9G8 on cytoplasmic RNA fate. 9G8 was shown to enhance expression of unspliced RNA containing either the Mason-Pfizer monkey virus-CTE or the recently discovered Tap-CTE. 9G8 also enhanced polyribosome association of unspliced RNA containing a CTE. Hyperphosphorylated 9G8 was present in monosomes and small polyribosomes, whereas soluble fractions contained only hypophosphorylated protein. Our results are consistent with a model in which hypophosphorylated SR proteins remain stably associated with messenger ribonucleoprotein ( mRNP) complexes during export and are released during translation initiation concomitant with increased phosphorylation. These results provide further evidence for crucial links between RNA splicing, export and translation.