The co-immunoprecipitation (co-IP) assay was performed as previously described (73 (link)). Briefly, 293T cells transfected with different plasmids or H358 cells infected with indicated viruses were lysed with lysis buffer (50mM Tris-HCl pH7.5, 150 mM NaCl, 1 mM EDTA, 1% Triton X-100) supplemented with protease inhibitor cocktail (Roche, 14826500) and phosphatase inhibitor cocktail (Sigma, 4906845001). Protein lysates were cleared by centrifugation at 12,000 g for 20 min at 4 °C. Supernatant was incubated with anti-Flag M2 beads (Sigma, F-2426) or anti-Myc beads (Sigma, E-6654) for 4h to overnight at 4 °C with gentle rotating. The beads were then washed once with lysis buffer, followed by additional three washes with wash buffer (50mM Tris-HCl pH7.5, 150 mM NaCl, 1 mM EDTA, 1% Triton X-100, 10% glycerol). The proteins were eluted by boiling in 2 × Laemmli sample buffer (65.8 mM Tris-HCl, pH 6.8, 2.1% SDS, 26.3% (w/v) glycerol, 355 mM b-mercaptoethanol, 0.01% bromophenol blue) and analyzed by SDS-PAGE and western blot.