Figure 2.

Schematic diagram of the generation of RNA polymerase I constructs. cDNAs derived from influenza virus were amplified by PCR, digested with BsmBI, and cloned into the BsmBI sites of the pHH21 vector (34), which contains the human RNA polymerase I promoter (P) and the mouse RNA polymerase I terminator (T). The thymidine nucleotide upstream of the terminator sequence (*T) represents the 3′ end of the influenza viral RNA. Influenza A virus sequences are shown in boldface letters.