Zhang Zhenyu, Aziati Ishmael D, Nipper Thomas, Boon Adrianus C M, Mehle Andrew
Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Department of Medicine, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA.
J Virol. 2025 Jun 17;99(6):e0052225. doi: 10.1128/jvi.00522-25. Epub 2025 May 14.
Bourbon virus (BRBV) is a tick-borne virus in the genus in the family. BRBV was initially identified as the presumptive causative agent of a fatal human infection in 2014 and has since been identified in ticks in the Midwest, Northeast, and Southern United States, with occasional spillovers into humans. However, little is known about how virus-host interactions impact their large host range. Here, we show that BRBV polymerase activity in human cells is completely dependent on cellular ANP32 proteins. BRBV polymerase activity was completely lost in cells lacking ANP32A and ANP32B, resulting in failed infections. BRBV polymerase activity was restored in the presence of ANP32 proteins from diverse hosts. Dhori virus and Thogoto virus, other related members, retained high activity in the absence of ANP32 proteins, showing reduced dependence on these host factors. Interaction studies revealed that the BRBV polymerase trimer binds human ANP32A or ANP32B. Genetic analysis revealed that tick vectors for BRBV encode a single locus corresponding to . Tick produces multiple protein variants through alternative splicing and start-site selection, all of which enhance polymerase activity for . Unexpectedly, the BRBV polymerase was highly sensitive to changes at the N-terminus of ANP32, while it was insensitive to changes in the body of ANP32 that restrict the activity of influenza virus polymerases. Thus, ANP32A is a deeply conserved pro-viral cofactor, and show remarkable plasticity utilizing ANP32 homologs from different hosts separated by almost 1 billion years of evolution.IMPORTANCEViral polymerases rely on cellular cofactors to support efficient transcription of viral genes and replication of the viral genome. The RNA-dependent RNA polymerase of influenza virus, an orthomyxovirus, requires the cellular ANP32A or ANP32B proteins for genome replication. However, little is known about whether ANP32 proteins are required by other orthomyxovirus family members, like the tick-borne thogotoviruses. We show that thogotoviruses use ANP32 proteins from diverse hosts to enhance polymerase activity, including that encoded by the single gene found in ticks. However, thogotovirus polymerase showed varying levels of dependence on ANP32 proteins, with some polymerases functioning at near full activity even in the absence of ANP32 proteins. Thus, ANP32 proteins are deeply conserved viral cofactors, with each virus displaying distinct patterns of ANP32 usage and requirements for function.
波旁病毒（BRBV）是布尼亚病毒科布尼亚病毒属的一种蜱传病毒。BRBV最初在2014年被确定为一例致命人类感染的推定病原体，此后在美国中西部、东北部和南部的蜱虫中被发现，偶尔会传播给人类。然而，关于病毒与宿主的相互作用如何影响其广泛的宿主范围，我们所知甚少。在此，我们表明BRBV在人类细胞中的聚合酶活性完全依赖于细胞ANP32蛋白。在缺乏ANP32A和ANP32B的细胞中，BRBV聚合酶活性完全丧失，导致感染失败。在存在来自不同宿主的ANP32蛋白时，BRBV聚合酶活性得以恢复。多里病毒和托戈托病毒是其他相关的布尼亚病毒科成员，在缺乏ANP32蛋白的情况下仍保持高活性，表明它们对这些宿主因子的依赖性较低。相互作用研究表明，BRBV聚合酶三聚体与人类ANP32A或ANP32B结合。遗传分析表明，BRBV的蜱传播媒介编码一个与ANP32相对应的单一位点。蜱虫的ANP32通过可变剪接和起始位点选择产生多种蛋白质变体，所有这些变体都增强了BRBV的聚合酶活性。出乎意料的是，BRBV聚合酶对ANP32的N端变化高度敏感，而对限制流感病毒聚合酶活性的ANP32主体部分的变化不敏感。因此，ANP32A是一种高度保守的病毒辅助因子，并且布尼亚病毒科病毒利用来自不同宿主的ANP32同源物表现出显著的可塑性，这些宿主在进化上相隔近10亿年。
重要性
病毒聚合酶依赖细胞辅助因子来支持病毒基因的有效转录和病毒基因组的复制。正粘病毒科的流感病毒的RNA依赖性RNA聚合酶需要细胞ANP32A或ANP32B蛋白进行基因组复制。然而，对于其他正粘病毒科成员，如蜱传托戈托病毒，是否需要ANP32蛋白，我们所知甚少。我们表明，托戈托病毒利用来自不同宿主的ANP32蛋白来增强聚合酶活性，包括蜱虫中发现的单个ANP32基因所编码的蛋白。然而，托戈托病毒聚合酶对ANP32蛋白的依赖性程度各不相同，有些聚合酶即使在没有ANP32蛋白的情况下也能以接近完全的活性发挥作用。因此，ANP32蛋白是高度保守的病毒辅助因子，每种病毒在ANP32的使用和功能需求方面都表现出独特的模式。
