Human cellular protein nucleoporin hNup98 interacts with influenza A virus NS2/nuclear export protein and overexpression of its GLFG repeat domain can inhibit virus propagation

The non-structural protein NS2, also called nuclear export protein, of influenza A virus contains a leucine-rich nuclear-export signal that could guide viral ribonucleoproteins to cross the nuclear pore complex (NPC) and complete directional nucleocytoplasmic trafficking. In this study, human nucleoporin 98 (hNup98), an NPC protein, was identified as an NS2-binding protein by using yeast two-hybrid screening of a human cDNA library. Interaction between NS2 and hNup98 was confirmed in yeast and mammalian cells. Mapping tests further demonstrated that aa 22–53 in the N-terminal region of NS2 and the glycine-leucine-phenylalanine-glycine (GLFG) repeat domain (aa 1–511) of hNup98 are crucial for the interaction of these two proteins. Confocal microscopy showed that hNup98 could specifically recruit NS2 to the nucleoli and that this process was inhibited by leptomycin B, a specific inhibitor of human chromosomal region maintenance 1 protein. NS2 recruitment to the nucleoli was through the N-terminal GLFG repeat domain of hNup98, but not through the C-terminal domain. Moreover, influenza virus infection downregulated Nup98 levels significantly in 293T and Madin–Darby canine kidney cells. Overexpression of the GLFG repeat domain of hNup98 apparently inhibited virus propagation. Together, these findings reveal the interaction between hNup98 and NS2. The GLFG repeat domain of hNup98 might competitively inhibit the interaction between NS2 and endogenous hNup98, consequently inhibiting virus propagation.