FIG. 1.

Identification of host NF90 association with influenza viral NP by MS. (A) HEK 293T cells were transfected with expression vectors for A/Vietnam/1194/04 (H5N1) NP-Flag and cultured for 48 h. Cell lysate was precipitated with α-Flag M2 (Sigma) monoclonal antibody, and precipitates were separated by SDS-PAGE and visualized by silver staining. Each of the separated protein bands was individually excised and analyzed by MS. (B) All resulting MS and MS/MS spectra were searched against human and virus databases. Three peptides detected from a band at the 90-kDa position indicated the identity of NF90 protein; the peptide sequences identified covered 5.3% of the NF90 protein sequence, and the MS/MS spectra matched NF90 with a >99% confidence interval. (C) Illustration of different NF90 isoforms.