Department of Biochemistry, University of Utah, Salt Lake City, United States.
Elife. 2024 May 15;13:RP93979. doi: 10.7554/eLife.93979.
Invertebrates use the endoribonuclease Dicer to cleave viral dsRNA during antiviral defense, while vertebrates use RIG-I-like Receptors (RLRs), which bind viral dsRNA to trigger an interferon response. While some invertebrate Dicers act alone during antiviral defense, Dicer acts in a complex with a dsRNA binding protein called RDE-4, and an RLR ortholog called DRH-1. We used biochemical and structural techniques to provide mechanistic insight into how these proteins function together. We found RDE-4 is important for ATP-independent and ATP-dependent cleavage reactions, while helicase domains of both DCR-1 and DRH-1 contribute to ATP-dependent cleavage. DRH-1 plays the dominant role in ATP hydrolysis, and like mammalian RLRs, has an N-terminal domain that functions in autoinhibition. A cryo-EM structure indicates DRH-1 interacts with DCR-1's helicase domain, suggesting this interaction relieves autoinhibition. Our study unravels the mechanistic basis of the collaboration between two helicases from typically distinct innate immune defense pathways.
无脊椎动物在抗病毒防御中使用内切核酸酶 Dicer 切割病毒 dsRNA，而脊椎动物则使用 RIG-I 样受体 (RLR)，后者结合病毒 dsRNA 以触发干扰素反应。虽然一些无脊椎动物 Dicer 在抗病毒防御中单独作用，但 Dicer 与一种称为 RDE-4 的 dsRNA 结合蛋白和一种称为 DRH-1 的 RLR 同源物形成复合物。我们使用生化和结构技术提供了这些蛋白质如何协同作用的机制见解。我们发现 RDE-4 对于 ATP 非依赖性和 ATP 依赖性切割反应很重要，而 DCR-1 和 DRH-1 的解旋酶结构域都有助于 ATP 依赖性切割。DRH-1 在 ATP 水解中起主导作用，并且与哺乳动物 RLR 一样，具有在自动抑制中起作用的 N 端结构域。低温电镜结构表明 DRH-1 与 DCR-1 的解旋酶结构域相互作用，表明这种相互作用可解除自动抑制。我们的研究揭示了两种来自典型不同先天免疫防御途径的解旋酶之间协作的机制基础。
