Escherichia coli factor Y sites of plasmid pBR322 can function as origins of DNA replication

The Escherichia coli replication factor Y, in conjunction with other genetically undefined E. coli replication factors and the gene products of the E. coli dnaB, dnaC, and dnaG loci, is involved in de novo primer formation on the phi X174 (+) single-strand circular DNA template [(+) ss(c)DNA]. The participation of factor Y in this series of reactions is correlated with its phi X174 (+) ss(c)-specific DNA-dependent ATPase activity. Recently two factor Y effector DNA segments of the plasmid pBR322 have been identified in close proximity to the plasmid origin of DNA replication. We report here that insertion of these factor Y sites into the filamentous phage f1R229 (+) ss(c)DNA confers upon it the ability to be converted to RF DNA in vitro through a rifampicin-resistant dnaB, dnaC, and dnaG gene product-dependent pathway. Our data suggest that factor Y effector sites can function as origins of DNA replication.