FIG. 1.

A/PR/8/34 viruses with mutations in the NS1 gene. (A) Schematic representation of functional domains of NS1 and the inactivating mutations. The functional amino acids are indicated by bold letters. The RNA-binding domain (positions 1 to 73) was inactivated by mutation R38A. CPSF binding in the effector domain (positions 74 to 230) was abolished by mutations F103S, M106I, and G184R. NS1(R/SI/G) represents wild-type NS1 of A/PR/8/34. (B) Subcellular localization of NP and NS1 in virus-infected cells. A549 cells were infected with the recombinant viruses at an MOI of 0.25. At 8 h p.i. the cells were fixed and stained with a polyclonal rabbit antiserum directed against NP and a monoclonal mouse antibody (1A7) directed against NS1. One representative result out of three independent experiments is shown.