Qiu Qian, He Zihan, Liu Jing, Xu Huijun, Wang Jinyu, Liu Nannan, Kang Ning, Pan Shaokun, Yu Weien, Gao Zixiang, Zhang Shimei, Yang Yang, Deng Qiang, Xie Youhua, Zhang Jiming, Shen Zhongliang
Department of Infectious Diseases, Shanghai Institute of Infectious Diseases and Biosecurity, Shanghai Key Laboratory of Infectious Diseases and Biosafety Emergency Response, National Medical Center for Infectious Diseases, Huashan Hospital, Fudan University, Shanghai, China.
Department of Microbiology and Parasitology, School of Basic Medical Sciences, Shanghai Medical College, Key Laboratory of Medical Molecular Virology (Ministry of Education/National Health Commission/Chinese Academy of Medical Sciences), Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, China.
PLoS Pathog. 2025 Jan 30;21(1):e1012897. doi: 10.1371/journal.ppat.1012897. eCollection 2025 Jan.
Hepatitis B virus (HBV) X protein (HBx) is a key factor for regulating viral transcription and replication. We recently characterized homeobox protein MSX-1 (MSX1) as a host restriction factor that inhibits HBV gene expression and genome replication by directly binding to HBV enhancer II/core promoter (EnII/Cp) and suppressing its promoter and enhancer activities. Notably, HBx expression was observed to be repressed more drastically by MSX1 compared to other viral antigens. In this work, we report that in addition to transcriptional repression, MSX1 also post-transcriptionally downregulates HBx protein stability. Mechanistically, MSX1 induces ubiquitin-independent proteasomal degradation of HBx, which is mediated through HBx C-terminal domain. Furthermore, this effect on HBx degradation correlates with MSX1-induced upregulation of DNAJA4 and CRYAB expression. Similar to MSX1, both DNAJA4 and CRYAB promote HBx degradation and repress HBV gene expression and genome replication. In chronic hepatitis B (CHB) patients, immune active phase (IA) is associated with higher intrahepatic expression of MSX1, DNAJA4 and CRYAB, and lower serum HBV markers compared to immune tolerant (IT) phase. Finally, HBV infection is significantly suppressed by MSX1 overexpression in both NTCP-overexpressing cell and humanized liver mouse models. These results demonstrate additional and novel mechanisms of MSX1-mediated repression of HBV, and establish MSX1 as a multi-functional HBV restriction factor with therapeutic potential.
乙型肝炎病毒（HBV）X蛋白（HBx）是调节病毒转录和复制的关键因子。我们最近鉴定了同源框蛋白MSX-1（MSX1）作为一种宿主限制因子，它通过直接结合HBV增强子II/核心启动子（EnII/Cp）并抑制其启动子和增强子活性来抑制HBV基因表达和基因组复制。值得注意的是，与其他病毒抗原相比，MSX1对HBx表达的抑制更为显著。在这项研究中，我们报告除了转录抑制外，MSX1还在转录后下调HBx蛋白的稳定性。机制上，MSX1诱导HBx的不依赖泛素的蛋白酶体降解，这是通过HBx的C末端结构域介导的。此外，这种对HBx降解的作用与MSX1诱导的DNAJA4和CRYAB表达上调相关。与MSX1类似，DNAJA4和CRYAB都促进HBx降解并抑制HBV基因表达和基因组复制。在慢性乙型肝炎（CHB）患者中，与免疫耐受（IT）期相比，免疫活跃期（IA）与肝内MSX1、DNAJA4和CRYAB的较高表达以及较低的血清HBV标志物相关。最后，在过表达NTCP的细胞和人源化肝脏小鼠模型中，MSX1的过表达均显著抑制了HBV感染。这些结果证明了MSX1介导的HBV抑制的额外和新机制，并将MSX1确立为具有治疗潜力的多功能HBV限制因子。
