Jia Jie, Arif Abul, Ray Partho S, Fox Paul L
Department of Cell Biology, The Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Mol Cell. 2008 Mar 28;29(6):679-90. doi: 10.1016/j.molcel.2008.01.010.
The heterotetrameric GAIT complex suppresses translation of selected mRNAs in interferon-gamma-activated monocytic cells. Specificity is dictated by glutamyl-prolyl tRNA synthetase (EPRS) binding to a 3'UTR element in target mRNAs. EPRS consists of two synthetase cores joined by a linker containing three WHEP domains of unknown function. Here we show the critical role of EPRS WHEP domains in targeting and regulating GAIT complex binding to RNA. The upstream WHEP pair directs high-affinity binding to GAIT element-bearing mRNAs, while the overlapping, downstream pair binds NSAP1, which inhibits mRNA binding. Interaction of EPRS with ribosomal protein L13a and GAPDH induces a conformational switch that rescues mRNA binding and restores translational control. Total reconstitution from purified components indicates that the four GAIT proteins are necessary and sufficient for self-assembly of a functional complex. Our results establish the essentiality of WHEP domains in the noncanonical function of EPRS in regulating inflammatory gene expression.
异源四聚体GAIT复合物可抑制干扰素-γ激活的单核细胞中特定mRNA的翻译。特异性由谷氨酰胺-脯氨酸tRNA合成酶（EPRS）与靶mRNA中的3'UTR元件结合决定。EPRS由两个合成酶核心组成，通过一个含有三个功能未知的WHEP结构域的接头连接。在这里，我们展示了EPRS WHEP结构域在靶向和调节GAIT复合物与RNA结合中的关键作用。上游的WHEP对指导与携带GAIT元件的mRNA的高亲和力结合，而重叠的下游对结合NSAP1，后者抑制mRNA结合。EPRS与核糖体蛋白L13a和甘油醛-3-磷酸脱氢酶（GAPDH）的相互作用诱导构象转换，从而挽救mRNA结合并恢复翻译控制。从纯化成分进行的完全重组表明，四种GAIT蛋白对于功能性复合物的自组装是必要且充分的。我们的结果确立了WHEP结构域在EPRS调节炎症基因表达的非经典功能中的必要性。
