BACKGROUND Bovine viral diarrhea virus (BVDV) belongs to the Flaviviridae family and the pestivius virus group. BVDV is responsible for significant economic loss in cattle industry worldwide because of reducing reproductive performance, increasing incidence of other diseases and mortality among young stock. The core (C) protein of the Flaviviridae family member is involved in host antiviral immune response through activation of related signaling pathways that affect the viral replication. However, the influence of C protein-interaction partners in BVDV infections is poorly defined. METHODS To explore C-protein-interacting partners, yeast two-hybrid was used to screen the interaction protein of C protein using bovine peripheral blood mononuclear cell (PBMC) cDNA library. The co-immunoprecipitation and confocal assays were manipulated to determine the interaction between potential partners and C protein. Knockdown and overexpression of the partner were used to examine whether the C-protein-interacting partner plays a role in BVDV proliferation and virulence. Meanwhile, qRT-PCR and western blot assays were used to investigate the effect of C protein and C-protein-interacting partner on the immune response of host cells. RESULTS We identified protein inhibitor of activated STAT 4 (PIAS4) as a novel interacting partner of the BVDV C protein. Co-immunoprecipitation and confocal assays demonstrated a strong interaction between C protein and PIAS4. Silencing of PIAS4 with small interfering RNA suppressed C protein expression and BVDV growth, while overexpression of PISA4 increased C protein expression and BVDV growth. The overexpression of PIAS4 increased the cell apoptosis. Meanwhile, the expressions of STAT4, SOCS3, IFITM, IFN-α were negatively regulated by the expression of PIAS4. The expression of C protein suppressed the antiviral proteins expression, and the inhibition effect was enhanced by interaction of PIAS4 and C protein. These results highlighted the beneficial properties of cellular PIAS4 for BVDV protein expression and growth. CONCLUSIONS This study provides reliable clues for understanding the roles of PIAS4 in the regulation of BVDV growth.

中文翻译：

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鉴定激活的STAT 4的蛋白抑制剂，该蛋白是与牛病毒性腹泻病毒生长有关的新型宿主相互作用伴侣。

背景技术牛病毒性腹泻病毒（BVDV）属于黄病毒科和瘟病毒属。由于降低了繁殖性能，增加了其他疾病的发病率并降低了年轻牲畜的死亡率，BVDV造成了全球养牛业的重大经济损失。黄病毒科成员的核心（C）蛋白通过激活影响病毒复制的相关信号通路参与宿主抗病毒免疫应答。但是，C蛋白相互作用伙伴在BVDV感染中的影响定义不清。方法为探索C蛋白相互作用的伴侣，采用酵母双杂交技术通过牛外周血单核细胞（PBMC）cDNA文库筛选C蛋白的相互作用蛋白。共免疫沉淀和共聚焦测定法可用于测定潜在伴侣和C蛋白之间的相互作用。敲除和伴侣的过表达用于检查与C蛋白相互作用的伴侣是否在BVDV增殖和毒力中起作用。同时，采用qRT-PCR和western blot方法研究了C蛋白和C蛋白相互作用伴侣对宿主细胞免疫反应的影响。结果我们确定了活化STAT 4（PIAS4）的蛋白抑制剂是BVDV C蛋白的新型相互作用伴侣。免疫共沉淀和共聚焦试验证明了C蛋白和PIAS4之间有很强的相互作用。用小的干扰RNA沉默PIAS4可抑制C蛋白表达和BVDV生长，而过表达PISA4可提高C蛋白表达和BVDV生长。PIAS4的过表达增加细胞凋亡。同时，STAT4，SOCS3，IFITM，IFN-α的表达受到PIAS4表达的负调控。C蛋白的表达抑制了抗病毒蛋白的表达，并且通过PIAS4和C蛋白的相互作用增强了抑制作用。这些结果突出了细胞PIAS4对于BVDV蛋白表达和生长的有益特性。结论本研究为理解PIAS4在BVDV生长调节中的作用提供了可靠的线索。PIAS4与C蛋白的相互作用增强了其抑制作用。这些结果突出了细胞PIAS4对于BVDV蛋白表达和生长的有益特性。结论本研究为理解PIAS4在BVDV生长调节中的作用提供了可靠的线索。PIAS4与C蛋白的相互作用增强了其抑制作用。这些结果突出了细胞PIAS4对BVDV蛋白表达和生长的有益特性。结论本研究为理解PIAS4在BVDV生长调节中的作用提供了可靠的线索。