富含甘氨酸和精氨酸 (GAR) 的基序常见于 RNA 结合和加工蛋白中，可通过蛋白质精氨酸甲基转移酶在精氨酸残基上对称 (SDMA) 或不对称 (ADMA) 二甲基化。精氨酸甲基化的蛋白质基序通常由含有 Tudor 结构域的蛋白质读取。在这里，我们使用 GFP-Trap 鉴定了一种非 Tudor 结构域蛋白，即 T 细胞 3 (SART3) 识别的鳞状细胞癌抗原，作为 SDMA 标记的 GAR 基序的读取器。 SART3 的结构分析和诱变表明，排列在两个相邻富含芳香族的半α四三肽 (HAT) 重复结构域之间的凹槽的芳香族残基对于 SART3 识别和结合 SDMA 标记的 GAR 基序肽以及SART3 与含有 GAR 基序的蛋白质原纤蛋白和线圈蛋白之间的相互作用。此外，我们发现这种阅读器能力的丧失会影响 RNA 剪接。总体而言，我们的研究结果扩大了潜在 SDMA 读者的范围，将 HAT 域包括在内。版权所有 © 2024 作者。由爱思唯尔公司出版。保留所有权利。

Glycine- and arginine-rich (GAR) motifs, commonly found in RNA-binding and -processing proteins, can be symmetrically (SDMA) or asymmetrically (ADMA) dimethylated at the arginine residue by protein arginine methyltransferases. Arginine-methylated protein motifs are usually read by Tudor domain-containing proteins. Here, using a GFP-Trap, we identify a non-Tudor domain protein, squamous cell carcinoma antigen recognized by T cells 3 (SART3), as a reader for SDMA-marked GAR motifs. Structural analysis and mutagenesis of SART3 show that aromatic residues lining a groove between two adjacent aromatic-rich half-a-tetratricopeptide (HAT) repeat domains are essential for SART3 to recognize and bind to SDMA-marked GAR motif peptides, as well as for the interaction between SART3 and the GAR-motif-containing proteins fibrillarin and coilin. Further, we show that the loss of this reader ability affects RNA splicing. Overall, our findings broaden the range of potential SDMA readers to include HAT domains.Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.