Virology Unit, Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare (THL), Mannerheimintie 166, FIN-00300 Helsinki, Finland.
Virol J. 2012 Aug 21;9:167. doi: 10.1186/1743-422X-9-167.
Influenza A virus non-structural protein 1 (NS1) is a virulence factor, which is targeted into the cell cytoplasm, nucleus and nucleolus. NS1 is a multi-functional protein that inhibits host cell pre-mRNA processing and counteracts host cell antiviral responses. Previously, we have shown that the NS1 protein of the H3N2 subtype influenza viruses possesses a C-terminal nuclear localization signal (NLS) that also functions as a nucleolar localization signal (NoLS) and targets the protein into the nucleolus.
Here, we show that the NS1 protein of the human H3N2 virus subtype interacts in vitro primarily via its C-terminal NLS2/NoLS and to a minor extent via its N-terminal NLS1 with the nucleolar proteins, nucleolin and fibrillarin. Using chimeric green fluorescence protein (GFP)-NS1 fusion constructs, we show that the nucleolar retention of the NS1 protein is determined by its C-terminal NLS2/NoLS in vivo. Confocal laser microscopy analysis shows that the NS1 protein colocalizes with nucleolin in nucleoplasm and nucleolus and with B23 and fibrillarin in the nucleolus of influenza A/Udorn/72 virus-infected A549 cells. Since some viral proteins contain NoLSs, it is likely that viruses have evolved specific nucleolar functions.
NS1 protein of the human H3N2 virus interacts primarily via the C-terminal NLS2/NoLS and to a minor extent via the N-terminal NLS1 with the main nucleolar proteins, nucleolin, B23 and fibrillarin.
甲型流感病毒非结构蛋白 1（NS1）是一种毒力因子，可靶向进入细胞质、细胞核和核仁。NS1 是一种多功能蛋白，可抑制宿主细胞的前体 mRNA 加工，并对抗宿主细胞的抗病毒反应。先前，我们已经表明，H3N2 亚型流感病毒的 NS1 蛋白具有一个 C 末端核定位信号（NLS），该信号还充当核仁定位信号（NoLS），并将蛋白靶向核仁。
在这里，我们表明，人 H3N2 病毒亚型的 NS1 蛋白主要通过其 C 末端 NLS2/NoLS 与核仁蛋白核仁磷蛋白和纤维蛋白发生体外相互作用，并在较小程度上通过其 N 末端 NLS1 与核仁蛋白发生相互作用。使用嵌合绿色荧光蛋白（GFP）-NS1 融合构建体，我们表明 NS1 蛋白在体内的核仁保留由其 C 末端 NLS2/NoLS 决定。共聚焦激光显微镜分析表明，NS1 蛋白与核磷蛋白和纤维蛋白在核质和核仁中以及与 B23 在流感 A/Udorn/72 病毒感染的 A549 细胞的核仁中发生共定位。由于一些病毒蛋白含有 NoLS，因此病毒可能已经进化出特定的核仁功能。
人 H3N2 病毒的 NS1 蛋白主要通过 C 末端 NLS2/NoLS 并在较小程度上通过 N 末端 NLS1 与主要核仁蛋白核磷蛋白、B23 和纤维蛋白相互作用。
