DNA polymerase β can substitute for DNA polymerase I in the initiation of plasmid DNA replication

We previously demonstrated that mammalian DNA polymerase β can substitute for DNA polymerase I of Escherichia coli in DNA replication and in base excision repair. We have now obtained genetic evidence suggesting that DNA polymerase β can substitute for E. coli DNA polymerase I in the initiation of replication of a plasmid containing a pMB1 origin of DNA replication. Specifically, we demonstrate that a plasmid with a pMB1 origin of replication can be maintained in an E. coli polA mutant in the presence of mammalian DNA polymerase β. Our results suggest that mammalian DNA polymerase β can substitute for E. coli DNA polymerase I by initiating DNA replication of this plasmid from the 3' OH terminus of the RNA-DNA hybrid at the origin of replication.