Tanaka Hiroki, Diogo Dias Joao, Jay Basile, Kita Shunsuke, Sasaki Mina, Takeda Hiroyuki, Kishimoto Naoki, Sasaki Shunsuke, Misumi Shogo, Mizokami Masashi, Neuveut Christine, Sumikama Takashi, Shibata Mikihiro, Maenaka Katsumi, Machida Shinichi
Department of Structural Virology, National Institute of Global Health and Medicine, Japan Institute for Health Security, Shinjuku-ku, Tokyo 162-8655, Japan.
Institut de Génétique Humaine, Laboratoire de Virologie Moléculaire, CNRS Université de Montpellier, Montpellier 34000, France.
Proc Natl Acad Sci U S A. 2025 Jun 17;122(24):e2421325122. doi: 10.1073/pnas.2421325122. Epub 2025 Jun 13.
A cure for chronic hepatitis B requires eliminating or permanently silencing covalently closed circular DNA (cccDNA). A pivotal target of this approach is the hepatitis B virus (HBV) X protein (HBx), which is a key factor that promotes transcription from cccDNA. However, the HBx structure remains unsolved. Here, we present the cryoelectron microscopy structure of HBx in complex with DDB1, which is an essential complex for cccDNA transcription. In this structure, hydrophobic interactions within HBx were identified, and mutational analysis highlighted their importance in the HBV life cycle. Our biochemical analysis revealed that the HBx-DDB1 complex directly interacts simultaneously with NSE3, which is a component of the SMC5/6 complex, and Spindlin1. Additionally, HBx-DDB1 complex dynamics were explored via high-speed atomic force microscopy. These findings provide comprehensive insights into the structure and function of HBx in HBV replication.
治愈慢性乙型肝炎需要消除或永久沉默共价闭合环状DNA（cccDNA）。这种方法的一个关键靶点是乙型肝炎病毒（HBV）X蛋白（HBx），它是促进cccDNA转录的关键因素。然而，HBx的结构仍未解析。在此，我们展示了与DDB1复合的HBx的冷冻电子显微镜结构，DDB1是cccDNA转录所必需的复合物。在该结构中，鉴定出了HBx内的疏水相互作用，突变分析突出了它们在HBV生命周期中的重要性。我们的生化分析表明，HBx-DDB1复合物直接同时与SMC5/6复合物的一个组分NSE3以及Spindlin1相互作用。此外，通过高速原子力显微镜探索了HBx-DDB1复合物的动力学。这些发现为HBx在HBV复制中的结构和功能提供了全面的见解。
