EWSR1 (Ewing Sarcoma Related protein 1) is an RNA binding protein that is ubiquitously expressed across cell lines and involved in multiple parts of RNA processing, such as transcription, splicing, and mRNA transport. EWSR1 has also been implicated in cellular mechanisms to control formation of R‐loops, a three‐stranded nucleic acid structure consisting of a DNA:RNA hybrid and a displaced single‐stranded DNA strand. Unscheduled R‐loops result in genomic and transcription stress. Loss of function of EWSR1 functions commonly found in Ewing Sarcoma correlates with high abundance of R‐loops. In this study, we investigated the mechanism for EWSR1 to recognize an R‐loop structure specifically. Using electrophoretic mobility shift assays (EMSA), we detected the high affinity binding of EWSR1 to substrates representing components found in R‐loops. EWSR1 specificity could be isolated to the DNA fork region, which transitions between double‐ and single‐stranded DNA. Our data suggests that the Zinc‐finger domain (ZnF) with flanking arginine and glycine rich (RGG) domains provide high affinity binding, while the RNA recognition motif (RRM) with its RGG domains offer improved specificity. This model offers a rational for EWSR1 specificity to encompass a wide range in contexts due to the DNA forks always found with R‐loops.

中文翻译：

---

尤文肉瘤相关蛋白 1 通过结合 DNA 叉识别 R 环

EWSR1（尤文肉瘤相关蛋白 1）是一种 RNA 结合蛋白，在细胞系中普遍表达，并参与 RNA 加工的多个部分，例如转录、剪接和 mRNA 运输。 EWSR1 还涉及控制 R 环形成的细胞机制，R 环是一种三链核酸结构，由 DNA:RNA 杂合体和置换的单链 DNA 链组成。计划外的 R 环会导致基因组和转录应激。尤文肉瘤中常见的 EWSR1 功能丧失与 R 环的高丰度相关。在本研究中，我们研究了 EWSR1 特异性识别 R 环结构的机制。使用电泳迁移率变动分析 (EMSA)，我们检测到 EWSR1 与代表 R 环中成分的底物的高亲和力结合。 EWSR1 特异性可以分离到 DNA 分叉区域，该区域在双链和单链 DNA 之间转换。我们的数据表明，侧翼富含精氨酸和甘氨酸（RGG）结构域的锌指结构域（ZnF）提供了高亲和力结合，而RNA识别基序（RRM）及其RGG结构域提供了更高的特异性。该模型为 EWSR1 特异性提供了合理的理由，使其能够涵盖广泛的背景，因为 DNA 叉总是与 R 环一起发现。