Shenzhen Key Laboratory for Systems Medicine in Inflammatory Diseases, School of Medicine, Shenzhen Campus of Sun Yat-Sen University, Sun Yat-Sen University, Shenzhen, China.
Department of General Surgery, Guangdong Institute of Gastroenterology, Guangdong Provincial Key Laboratory of Colorectal and Pelvic Floor Diseases, Biomedical Innovation Center, The Sixth Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.
Nat Struct Mol Biol. 2023 Aug;30(8):1183-1192. doi: 10.1038/s41594-023-01043-2. Epub 2023 Jul 24.
Influenza polymerase (FluPol) transcribes viral mRNA at the beginning of the viral life cycle and initiates genome replication after viral protein synthesis. However, it remains poorly understood how FluPol switches between its transcription and replication states, especially given that the structural bases of these two functions are fundamentally different. Here we propose a mechanism by which FluPol achieves functional switching between these two states through a previously unstudied conformation, termed an 'intermediate state'. Using cryo-electron microscopy, we obtained a structure of the intermediate state of H5N1 FluPol at 3.7 Å, which is characterized by a blocked cap-binding domain and a contracted core region. Structural analysis results suggest that the intermediate state may allow FluPol to transition smoothly into either the transcription or replication state. Furthermore, we show that the formation of the intermediate state is required for both the transcription and replication activities of FluPol, leading us to conclude that the transcription and replication cycles of FluPol are regulated via this intermediate state.
流感聚合酶（FluPol）在病毒生命周期的开始转录病毒 mRNA，并在病毒蛋白合成后启动基因组复制。然而，FluPol 如何在转录和复制状态之间切换仍然知之甚少，特别是考虑到这两种功能的结构基础在根本上是不同的。在这里，我们提出了一种机制，通过该机制，FluPol 通过一种以前未被研究的构象，即“中间状态”，在这两种状态之间实现功能切换。我们使用冷冻电子显微镜获得了 3.7 Å 的 H5N1 FluPol 中间状态的结构，其特征是封闭的帽结合结构域和收缩的核心区域。结构分析结果表明，中间状态可能允许 FluPol 平稳地过渡到转录或复制状态。此外，我们表明中间状态的形成对于 FluPol 的转录和复制活性都是必需的，这使我们得出结论，FluPol 的转录和复制循环是通过这种中间状态来调节的。
