Squatrito Massimo, Mancino Monica, Sala Leonardo, Draetta Giulio F
European Institute of Oncology, 435 Via Ripamonti, 20141 Milan, Italy.
Biochem Biophys Res Commun. 2006 Jun 9;344(3):859-68. doi: 10.1016/j.bbrc.2006.03.205. Epub 2006 Apr 19.
dsRNA-binding domains (dsRBDs) characterize an expanding family of proteins involved in different cellular processes, ranging from RNA editing and processing to translational control. Here we present evidence that Ebp1, a cell growth regulating protein that is part of ribonucleoprotein (RNP) complexes, contains a dsRBD and that this domain mediates its interaction with dsRNA. Deletion of Ebp1's dsRBD impairs its localization to the nucleolus and its ability to form RNP complexes. We show that in the cytoplasm, Ebp1 is associated with mature ribosomes and that it is able to inhibit the phosphorylation of serine 51 in the eukaryotic initiation factor 2 alpha (eIF2alpha). In response to various cellular stress, eIF2alpha is phosphorylated by distinct protein kinases (PKR, PERK, GCN2, and HRI), and this event results in protein translation shut-down. Ebp1 overexpression in HeLa cells is able to protect eIF2alpha from phosphorylation at steady state and also in response to various treatments. We demonstrate that Ebp1 interacts with and is phosphorylated by the PKR protein kinase. Our results demonstrate that Ebp1 is a new dsRNA-binding protein that acts as a cellular inhibitor of eIF2alpha phosphorylation suggesting that it could be involved in protein translation control.
双链RNA结合结构域（dsRBDs）是一类不断扩大的蛋白质家族的特征，这些蛋白质参与从RNA编辑和加工到翻译控制等不同的细胞过程。在此，我们提供证据表明，作为核糖核蛋白（RNP）复合物一部分的细胞生长调节蛋白Ebp1含有一个dsRBD，并且该结构域介导其与双链RNA的相互作用。删除Ebp1的dsRBD会损害其在核仁中的定位及其形成RNP复合物的能力。我们表明，在细胞质中，Ebp1与成熟核糖体相关联，并且它能够抑制真核起始因子2α（eIF2α）中丝氨酸51的磷酸化。响应各种细胞应激，eIF2α被不同的蛋白激酶（PKR、PERK、GCN2和HRI）磷酸化，这一事件导致蛋白质翻译关闭。在HeLa细胞中过表达Ebp1能够在稳态以及响应各种处理时保护eIF2α不被磷酸化。我们证明Ebp1与PKR蛋白激酶相互作用并被其磷酸化。我们的结果表明，Ebp1是一种新的双链RNA结合蛋白，作为eIF2α磷酸化的细胞抑制剂，表明它可能参与蛋白质翻译控制。
