Methylarginines within the RGG-Motif Region of hnRNP A1 Affect Its IRES Trans-Acting Factor Activity and Are Required for hnRNP A1 Stress Granule Localization and Formation.
Methylarginines within the RGG-Motif Region of hnRNP A1 Affect Its IRES Trans-Acting Factor Activity and Are Required for hnRNP A1 Stress Granule Localization and Formation.
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DOI：
10.1016/j.jmb.2016.12.011
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发表时间：
2017-01
影响因子：
5.6
通讯作者：
Michael L. Wall;S. M. Lewis
中科院分区：
文献类型：
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作者：
Michael L. Wall;S. M. Lewis
异质核核糖核蛋白A1（hnRNPA 1）是一种应激颗粒相关的RNA结合蛋白，在细胞凋亡和细胞应激恢复中起作用。HnRNP A1是蛋白质精氨酸甲基转移酶1的主要非组蛋白靶标，其在其精氨酸-甘氨酸-甘氨酸（RGG）基序区域内的几个关键精氨酸残基处不对称地二甲基化hnRNP A1。虽然已知精氨酸甲基化在体外调节hnRNP A1的一般RNA结合，但精氨酸甲基化在hnRNP A1胞质活性中的功能作用尚不清楚。为了测试关键甲基精氨酸残基对hnRNP A1细胞质活性和应激颗粒缔合的影响，产生了hnRNP A1的细胞质限制性Flag标记的突变体，其中RGG基序区域内的关键甲基精氨酸残基被改变为赖氨酸或丙氨酸。赖氨酸取代，模拟未甲基化精氨酸，导致内部核糖体进入位点反式作用因子（ITAF）活性增加40%，该蛋白质容易与应激颗粒相关联。丙氨酸取代导致ITAF活性丧失和mRNA结合减少。丙氨酸突变体还显示减少的应激颗粒缔合并抑制应激颗粒形成。我们的数据表明，精氨酸残基的RGG基序区域内的hnRNP A1细胞质的活动是至关重要的，内源性的不对称二甲基化的RGG基序区域抑制hnRNP A1 ITAF活性在细胞中。我们的研究结果表明，甲基精氨酸残基的RGG基序区域内的hnRNP A1是重要的，其细胞质的活动和低甲基化和/或突变的RGG基序区域可能有助于hnRNP A1在疾病，如癌症的作用。
Heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is a stress granule-associated RNA-binding protein that plays a role in apoptosis and cellular stress recovery. HnRNP A1 is a major non-histone target of protein arginine methyltransferase 1, which asymmetrically dimethylates hnRNP A1 at several key arginine residues within its arginine–glycine–glycine (RGG)-motif region. Although arginine methylation is known to regulate general RNA binding of hnRNP A1in vitro, the functional role of arginine methylation in hnRNP A1 cytoplasmic activity is unknown. To test the impact of key methylarginine residues on hnRNP A1 cytoplasmic activity and stress granule association, cytoplasmically restricted Flag-tagged mutants of hnRNP A1 were generated in which key methylarginine residues within the RGG-motif region were changed to either lysine or alanine. Lysine substitution, which mimics unmethylated arginine, resulted in a 40% increase in internal ribosome entry sitetrans-acting factor (ITAF) activity and the protein readily associates with stress granules. Alanine substitution resulted in a loss of ITAF activity and reduced mRNA binding. The alanine mutant also displays reduced stress granule association and suppresses stress granule formation. Our data suggest that arginine residues within the RGG-motif region are critical for hnRNP A1 cytoplasmic activities and that endogenous asymmetric dimethylation of the RGG-motif region suppresses hnRNP A1 ITAF activity in cells. Our findings indicate that methylarginine residues within the RGG-motif region of hnRNP A1 are important for its cytoplasmic activities and that hypomethylation and/or mutation of the RGG-motif region may contribute to the role of hnRNP A1 in diseases such as cancer.