Nonstructural protein 1 (NS1) of the influenza A virus is a major contributor to the virulence of the seasonal influenza A viruses, in part because it interferes with host viral defense mechanisms. SUMOylation regulates NS1 activity, and several residues of NS1 have been identified with traditional biochemical approaches as acceptor sites for SUMOylation. In this study, we developed a novel FRET assay to assess SUMOylation. Using this assay, we demonstrated that the lysine residue K131 in the effector domain of NS1 is a previously unidentified SUMO acceptor site. A recombinant H1N1 influenza A virus (A/PR/8/34) expressing a K131 SUMOylation–deficient NS1 had a significantly lower growth rate than the wild-type virus. These results suggest that NS1 SUMOylation at K131 is required for the rapid replication of H1N1 influenza viruses. The interaction between the NS1 protein and the host SUMOylation components may serve as a novel target for the development of anti–influenza A drugs.

甲型流感病毒的非结构蛋白 1 (NS1) 是季节性甲型流感病毒毒力的主要贡献者，部分原因是它干扰宿主病毒防御机制。SUMOylation 调节 NS1 活性，并且已经使用传统的生化方法鉴定了 NS1 的几个残基作为 SUMOylation 的受体位点。在这项研究中，我们开发了一种新的 FRET 检测来评估 SUMOylation。使用该测定，我们证明了 NS1 效应域中的赖氨酸残基 K131 是以前未鉴定的 SUMO 受体位点。表达 K131 SUMOylation 缺陷型 NS1 的重组 H1N1 甲型流感病毒 (A/PR/8/34) 的生长速度明显低于野生型病毒。这些结果表明 H1N1 流感病毒的快速复制需要 K131 处的 NS1 SUMOylation。