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The RNA-Binding Domain of hnRNP U Extends beyond the RGG/RG Motifs
Biochemistry ( IF 2.9 ) Pub Date : 2024-02-08 , DOI: 10.1021/acs.biochem.3c00510
Otto A Kletzien 1 , Deborah S Wuttke 1 , Robert T Batey 1
Affiliation  

Heterogeneous nuclear ribonucleoprotein U (hnRNP U) is a ubiquitously expressed protein that regulates chromatin architecture through its interactions with numerous DNA, protein, and RNA partners. The RNA-binding domain (RBD) of hnRNP U was previously mapped to an RGG/RG motif within its disordered C-terminal region, but little is understood about its binding mode and potential for selective RNA recognition. Analysis of publicly available hnRNP U enhanced UV cross-linking and immunoprecipitation (eCLIP) data identified high-confidence binding sites within human RNAs. We synthesized a set of diverse RNAs encompassing 11 of these identified cross-link sites for biochemical characterization using a combination of fluorescence anisotropy and electrophoretic mobility shift assays. These in vitro binding experiments with a rationally designed set of RNAs and hnRNP U domains revealed that the RGG/RG motif is a small part of a more expansive RBD that encompasses most of the disordered C-terminal region. This RBD contains a second, previously experimentally uncharacterized RGG/RG motif with RNA-binding properties comparable to those of the canonical RGG/RG motif. These RGG/RG motifs serve redundant functions, with neither serving as the primary RBD. While in isolation, each RGG/RG motif has modest affinity for RNA, together they significantly enhance the association of hnRNP U with RNA, enabling the binding of most of the designed RNA set with low to midnanomolar binding affinities. Identification and characterization of the complete hnRNP U RBD highlight the perils of a reductionist approach to defining biochemical activities in this system and pave the way for a detailed investigation of its RNA-binding specificity.

中文翻译:


hnRNP U 的 RNA 结合结构域超越了 RGG/RG 基序



异质核核糖核蛋白 U (hnRNP U) 是一种普遍表达的蛋白质,通过与众多 DNA、蛋白质和 RNA 伴侣的相互作用来调节染色质结构。hnRNP U 的 RNA 结合结构域 (RBD) 以前被定位到其无序 C 末端区域内的 RGG/RG 基序,但对其结合模式和选择性 RNA 识别的潜力知之甚少。对公开可用的 hnRNP U 增强型 UV 交联和免疫沉淀 (eCLIP) 数据的分析确定了人 RNA 中的高置信度结合位点。我们合成了一组不同的 RNA,其中包含其中 11 个已鉴定的交联位点,用于使用荧光各向异性和电泳迁移率变化测定的组合进行生化表征。这些使用合理设计的 RNA 和 hnRNP U 结构域进行的体外结合实验表明,RGG/RG 基序是包含大部分无序 C 末端区域的更广阔的 RBD 的一小部分。该 RBD 包含第二个先前未在实验中表征的 RGG/RG 基序,其 RNA 结合特性与经典 RGG/RG 基序相当。这些 RGG/RG 基序具有冗余功能,都不作为主要的 RBD。在分离时,每个 RGG/RG 基序对 RNA 具有适度的亲和力,它们共同显著增强了 hnRNP U 与 RNA 的结合,从而能够以低至中纳摩尔结合亲和力结合大多数设计的 RNA 组结合。完整 hnRNP U RBD 的鉴定和表征突出了还原论方法定义该系统中生化活性的危险,并为详细研究其 RNA 结合特异性铺平了道路。
更新日期:2024-02-08
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