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 replication. 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 and for the R6K plasmid. 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.