Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA.
Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
RNA. 2018 May;24(5):688-703. doi: 10.1261/rna.063313.117. Epub 2018 Feb 7.
Astrocyte elevated gene-1 (AEG-1), an oncogene whose overexpression promotes tumor cell proliferation, angiogenesis, invasion, and enhanced chemoresistance, is thought to function primarily as a scaffolding protein, regulating PI3K/Akt and Wnt/β-catenin signaling pathways. Here we report that AEG-1 is an endoplasmic reticulum (ER) resident integral membrane RNA-binding protein (RBP). Examination of the AEG-1 RNA interactome by HITS-CLIP and PAR-CLIP methodologies revealed a high enrichment for endomembrane organelle-encoding transcripts, most prominently those encoding ER resident proteins, and within this cohort, for integral membrane protein-encoding RNAs. Cluster mapping of the AEG-1/RNA interaction sites demonstrated a normalized rank order interaction of coding sequence >5' untranslated region, with 3' untranslated region interactions only weakly represented. Intriguingly, AEG-1/membrane protein mRNA interaction sites clustered downstream from encoded transmembrane domains, suggestive of a role in membrane protein biogenesis. Secretory and cytosolic protein-encoding mRNAs were also represented in the AEG-1 RNA interactome, with the latter category notably enriched in genes functioning in mRNA localization, translational regulation, and RNA quality control. Bioinformatic analyses of RNA-binding motifs and predicted secondary structure characteristics indicate that AEG-1 lacks established RNA-binding sites though shares the property of high intrinsic disorder commonly seen in RBPs. These data implicate AEG-1 in the localization and regulation of secretory and membrane protein-encoding mRNAs and provide a framework for understanding AEG-1 function in health and disease.
星形胶质细胞上调基因-1（AEG-1）是一种癌基因，其过表达可促进肿瘤细胞增殖、血管生成、侵袭和增强化疗耐药性，被认为主要作为支架蛋白发挥作用，调节 PI3K/Akt 和 Wnt/β-catenin 信号通路。在这里，我们报告 AEG-1 是内质网（ER）驻留的完整膜 RNA 结合蛋白（RBP）。通过 HITS-CLIP 和 PAR-CLIP 方法检查 AEG-1 RNA 相互作用组，发现富含内质网驻留蛋白编码转录本，尤其是那些编码内质网驻留蛋白的转录本，并且在这个队列中，还包含编码完整膜蛋白的 RNA。AEG-1/RNA 相互作用位点的聚类映射显示编码序列>5'非翻译区的归一化等级相互作用，而 3'非翻译区相互作用则较弱。有趣的是，AEG-1/膜蛋白 mRNA 相互作用位点聚类在编码跨膜结构域的下游，提示其在膜蛋白生物发生中的作用。分泌蛋白和胞质蛋白编码的 mRNA 也存在于 AEG-1 RNA 相互作用组中，后者在功能上显著富集于参与 mRNA 定位、翻译调控和 RNA 质量控制的基因。RNA 结合基序和预测二级结构特征的生物信息学分析表明，AEG-1 缺乏已建立的 RNA 结合位点，但具有 RBPs 中常见的高固有无序特性。这些数据表明 AEG-1 参与了分泌蛋白和膜蛋白编码 mRNA 的定位和调节，并为理解 AEG-1 在健康和疾病中的功能提供了框架。
