A plasmid that improves the efficiency of foreign gene expression by intracellular T7 RNA polymerase.

To facilitate the construction of recombinant plasmids for expressing cloned genes with T7 RNA polymerase supplied by recombinant vaccinia virus, a plasmid expression vector was designed by combining parts of plasmids pTZ18R, pBluescript II KS+, and pAR2529. The 3043-bp plasmid pTF1 has a T7 RNA polymerase promoter, multiple cloning site for insertion of foreign genes, and a T7-specific transcription termination signal. Plasmid pTF1 had several advantages compared with the reference plasmid pAR2529, including more efficient replication in bacteria, greater flexibility in the insertion and subcloning of foreign genes, and increased efficiency of liposome-mediated introduction into cultured cells for expression of the foreign gene.