Chang Yu, Shan Zhibo, Shi Wenjun, Li Qibing, Wang Yihan, Wang Bo, Wang Guangwen, Chen Hualan, Jiang Li, Li Chengjun
State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China.
Technology Center of Qingdao Customs, Qingdao 266000, China.
Viruses. 2025 May 4;17(5):671. doi: 10.3390/v17050671.
The transcription and replication of the genome of influenza A virus (IAV) take place in the nucleus of infected cells, which is catalyzed by the viral ribonucleoprotein (vRNP) complex. The nuclear import of the vRNP complex and its component proteins is essential for the efficient replication of IAV and is therefore prone to be targeted by host restriction factors. Herein, we found that host cellular protein keratin 6A (KRT6A) is a negative regulator of IAV replication because siRNA-mediated knockdown of expression increased the growth titers of IAV, whereas exogenous overexpression of KRT6A reduced viral yields. The nuclear import of incoming vRNP complexes and newly synthesized nucleoprotein (NP) was significantly impaired when KRT6A was overexpressed. Further studies showed that KRT6A interacts with the four vRNP complex proteins-polymerase basic protein 1 (PB1), polymerase basic protein 2 (PB2), polymerase acidic protein (PA), and NP. Notably, the interaction between KRT6A and vRNP complex proteins had no effect on the nuclear import of PB2 or the PB1-PA heterodimer but impaired the interaction between NP and the nuclear import adaptor importin α3, thereby inhibiting the nuclear import of incoming vRNP complexes and newly synthesized NP. Moreover, KRT6A was further shown to suppress the assembly of the vRNP complex and consequently reduce viral polymerase activity. Together, our data uncover a novel role of KRT6A in counteracting the nuclear import and functions of the vRNP complex, thereby restricting the replication of IAV.
甲型流感病毒（IAV）基因组的转录和复制在受感染细胞的细胞核中进行，由病毒核糖核蛋白（vRNP）复合体催化。vRNP复合体及其组成蛋白的核输入对于IAV的有效复制至关重要，因此容易受到宿主限制因子的靶向作用。在此，我们发现宿主细胞蛋白角蛋白6A（KRT6A）是IAV复制的负调节因子，因为小干扰RNA介导的KRT6A表达敲低增加了IAV的生长滴度，而KRT6A的外源性过表达降低了病毒产量。当KRT6A过表达时，进入的vRNP复合体和新合成的核蛋白（NP）的核输入受到显著损害。进一步研究表明，KRT6A与vRNP复合体的四种蛋白——聚合酶基本蛋白1（PB1）、聚合酶基本蛋白2（PB2）、聚合酶酸性蛋白（PA）和NP相互作用。值得注意的是，KRT6A与vRNP复合体蛋白之间的相互作用对PB2或PB1-PA异二聚体的核输入没有影响，但损害了NP与核输入衔接蛋白输入蛋白α3之间的相互作用，从而抑制了进入的vRNP复合体和新合成的NP的核输入。此外，进一步研究表明KRT6A抑制vRNP复合体的组装，从而降低病毒聚合酶活性。总之，我们的数据揭示了KRT6A在对抗vRNP复合体的核输入和功能方面的新作用，从而限制了IAV的复制。
