REPLICATION TERMINUS FOR DNA POLYMERASE I DURING INITIATION OF PAM-BETA-1 REPLICATION - ROLE OF THE PLASMID-ENCODED RESOLUTION SYSTEM

摘要

Replication of plasmid pAM beta 1 is initiated by DNA polymerase I (poi I) and completed by DNA polymerase III holoenzyme contained in the replisome machinery. In this study we report that initiation of DNA replication generates D-loop structures containing the nascent leading strand paired to its template, and that D-loop extension is arrested approximate to 230 bp from the initiation site of DNA synthesis in the presence of the plasmid-encoded resolvase. In vitro and in vivo data suggest that this arrest is caused by a collision between poi I and the resolvase bound to its target. As the arrested D-loop replication intermediates carry a single-stranded primosome-assembly site, we hypothesize that the biological role of the replication arrest is to limit the region replicated by poi I and to promote the replacement of poi I by the replisome in order to initiate concerted synthesis of the leading and lagging strands. [References: 48]