FIG. 2.

The pPolI-GFP plasmid for generating influenza virus-like RNA encoding the GFP protein. The GFP gene (derived from pEGFP-N1 [Clontech, Palo Alto, Calif.]) was inserted in the antisense orientation into pHL1844 (E. Hoffmann, Ph.D. thesis, Justus-Liebig University, Giessen, Germany), which contains the 5′ and 3′ noncoding regions of influenza A virus segment 5 (NP-NTRs). The gene was flanked by multiple cloning sites (MCS1 and MCS2) and by the human RNA polymerase I promoter and the mouse RNA polymerase I terminator. Asterisks indicate mutations introduced to upregulate promoter activity (10a).