SF2/ASF Regulates Proteomic Diversity by Affecting the Balance Between Translation Initiation Mechanisms
SF2/ASF Regulates Proteomic Diversity by Affecting the Balance Between Translation Initiation Mechanisms
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DOI：
10.1002/jcb.22181
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发表时间：
2009-07-01
影响因子：
4
通讯作者：
Srebrow, Anabella
中科院分区：
文献类型：
--
作者：
Blaustein, Matias;Quadrana, Leandro;Srebrow, Anabella
已经描述了一组穿梭的富含丝氨酸/精氨酸的剪接调控蛋白的剪接后活性，其中包括SF2/ASF。我们发现，生长因子激活了Ras-PI 3-Kinase-Akt/PKB信号通路，不仅修改了纤维连接蛋白EDA外显子的选择性剪接，而且还改变了含有SF2/ASF的EDA结合基序的报告mRNAs的体内翻译，提供了两种共同调节的异构体特异性扩增水平。大多数真核细胞mRNAs的翻译是通过扫描机制启动的，这意味着eIF4F蛋白复合体可以识别mRNA5‘末端的m7G帽。一些病毒和细胞的mRNAs以帽不依赖的方式被翻译，通过被称为内部核糖体进入位点的顺式作用的mRNA元件的作用，引导内部核糖体与mRNAs结合。在这里，我们使用双顺反子记者产生携带两个开放阅读框架的mRNAs，一个以帽子依赖的方式翻译，另一个通过内部核糖体进入位点依赖的方式翻译，以表明在体内过表达SF2/ASF增加了帽子依赖和内部核糖体进入位点依赖的翻译之间的比率。一贯地，SF2/ASF的击倒会产生相反的效果。SF2/ASF表达水平的变化也会影响编码成纤维细胞生长因子-2的内源性mRNA的选择性翻译。这些结果有力地表明了SF2/ASF作为选择性翻译的调节因子的作用，这意味着通过这两种翻译起始机制之间的平衡产生不同的蛋白质，并将SF2/ASF调节蛋白质组多样性的已知潜力扩展到翻译领域。J.细胞。生物化学。107：826-833,2009。(C)2009年Wiley-Liss，Inc.
Post-splicing activities have been described for a subset of shuttling serine/arginine-rich splicing regulatory proteins, among them SF2/ASF. We showed that growth factors activate a Ras-PI 3-kinase-Akt/PKB signaling pathway that not only modifies alternative splicing of the fibronectin EDA exon, but also alters in vivo translation of reporter mRNAs containing the EDA binding motif for SF2/ASF, providing two coregulated levels of isoform-specific amplification. Translation of most eukaryotic mRNAs is initiated via the scanning mechanism, which implicates recognition of the m7G cap at the mRNA 5'-terminus by the eIF4F protein complex. Several viral and cellular mRNAs are translated in a cap-independent manner by the action of cis-acting mRNA elements named internal ribosome entry sites that direct internal ribosome binding to the mRNA. Here we use bicistronic reporters that generate mRNAs carrying two open reading frames, one translated in a cap-dependent manner while the other by internal ribosome entry site-dependent initiation, to show that in vivo over-expression of SF2/ASF increases the ratio between cap-dependent and internal ribosome entry site-dependent translation. Consistently, knocking-down of SF2/ASF causes the opposite effect. Changes in expression levels of SF2/ASF also affect alternative translation of an endogenous mRNA, that one coding for fibroblast growth factor-2. These results strongly suggest a role for SF2/ASF as a regulator of alternative translation, meaning the generation of different proteins by the balance among these two translation initiation mechanisms, and expand the known potential of SF2/ASF to regulate proteomic diversity to the translation field. J. Cell. Biochem. 107: 826-833, 2009. (C) 2009 Wiley-Liss, Inc.