DNA-POLYMERASE-BETA CAN SUBSTITUTE FOR DNA-POLYMERASE-I IN THE INITIATION OF PLASMID DNA-REPLICATION

We previously demonstrated that mammalian DNA polymerase beta can subs titute for DNA polymerase I of Escherichia coli in DNA replication and in base excision repair. We have now obtained genetic evidence sugges ting that DNA polymerase beta can substitute for E. coli DNA polymeras e I in the initiation of replication of a plasmid containing a pMB1 or igin of DNA replication. Specifically, we demonstrate that a plasmid w ith a pMB1 origin of replication can be maintained in an E. coli polA mutant in the presence of mammalian DNA polymerase beta. Our results s uggest that mammalian DNA polymerase beta can substitute for E. coli D NA polymerase I by initiating DNA replication of this plasmid from the 3' OH terminus of the RNA-DNA hybrid at the origin of replication.