Lee Kong Chian School of Medicine, Nanyang Technological University, EMB 03-07, 59 Nanyang Drive 636921, Singapore.
School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive 637551, Singapore.
Nucleic Acids Res. 2021 Sep 27;49(17):9978-9991. doi: 10.1093/nar/gkab712.
DRH-3 is critically involved in germline development and RNA interference (RNAi) facilitated chromosome segregation via the 22G-siRNA pathway in Caenorhabditis elegans. DRH-3 has similar domain architecture to RIG-I-like receptors (RLRs) and belongs to the RIG-I-like RNA helicase family. The molecular understanding of DRH-3 and its function in endogenous RNAi pathways remains elusive. In this study, we solved the crystal structures of the DRH-3 N-terminal domain (NTD) and the C-terminal domains (CTDs) in complex with 5'-triphosphorylated RNAs. The NTD of DRH-3 adopts a distinct fold of tandem caspase activation and recruitment domains (CARDs) structurally similar to the CARDs of RIG-I and MDA5, suggesting a signaling function in the endogenous RNAi biogenesis. The CTD preferentially recognizes 5'-triphosphorylated double-stranded RNAs bearing the typical features of secondary siRNA transcripts. The full-length DRH-3 displays unique structural dynamics upon binding to RNA duplexes that differ from RIG-I or MDA5. These features of DRH-3 showcase the evolutionary divergence of the Dicer and RLR family of helicases.
DRH-3 对于线虫的生殖系发育和 RNA 干扰 (RNAi) 介导的染色体分离至关重要，其通过 22G-siRNA 途径发挥作用。DRH-3 的结构域架构与 RIG-I 样受体 (RLRs) 相似，属于 RIG-I 样 RNA 解旋酶家族。目前仍不清楚 DRH-3 的分子机制及其在内源性 RNAi 途径中的功能。在这项研究中，我们解析了与 5′-三磷酸化 RNA 结合的 DRH-3 N 端结构域 (NTD) 和 C 端结构域 (CTD) 的晶体结构。DRH-3 的 NTD 采用串联半胱天冬酶激活和募集结构域 (CARD) 的独特折叠，其结构与 RIG-I 和 MDA5 的 CARD 相似，提示其在内源性 RNAi 生物发生中具有信号功能。CTD 优先识别具有典型二级 siRNA 转录本特征的 5′-三磷酸化双链 RNA。全长 DRH-3 在与 RNA 双链结合时表现出独特的结构动力学，与 RIG-I 或 MDA5 不同。DRH-3 的这些特征展示了 Dicer 和 RLR 家族解旋酶的进化分歧。
