Plasmid R1 DNA replication dependent on protein synthesis in cell-free extracts of E. coli

Bacterial plasmids serve as model systems for studying the regulation of DNA replication¹. Elucidation of the molecular mechanisms involved in plasmid DNA synthesis requires the development of efficient cell-free plasmid replication systems. Such in vitro systems have previously only been described for Col E1-type plasmids^2,3 and for the R6K plasmid^4,5. Here we report that extracts of Escherichia coli can carry out the complete replication of miniplasmids derived from the antibiotic-resistance plasmid R1. This R1 replication system differs from the previously described ColE1 and R6K systems in its strict dependence on DNA-directed protein synthesis. We believe this to be the first report of the functional coupling of the three fundamental reactions of genetic information transfer (transcription, translation and replication) in a cell-free system.