Appearance of beta-lactamase activity in animal cells upon liposome-mediated gene transfer

A restriction fragment, 875 bp, which encodes for a beta-lactamase activity, was isolated from the Escherichia coli plasmid pBR322 DNA and entrapped in liposomes. The incubation of the DNA-liposomes with avian, murine, and human cultured cells results in the uptake of the DNA with the efficiency of around 2000 molecules per cell. Extracts of the recipient cells show a beta-lactamase activity as demonstrated by spectroscopic and microbiological methods. These results indicate the expression of a prokaryotic gene in eukaryotic cells.