Functional interactions of an archaeal sliding clamp with mammalian clamp loader and DNA polymerase delta

Background: By the total genome sequencing of several archaeal organisms, i t has been confirmed that many archaeal proteins related to genetic informa tion systems, including DNA replication, transcription and translation, hav e similar sequences to these of eukaryotes. In eukaryotic DNA replication, proliferating cell nuclear antigen (PCNA) works in clamping DNA polymerases on the DNA template and accomplishes a processive DNA synthesis. Archaea e ncode PCNA homologues in their genomes and Pyrococcus furiosus PCNA (PfuPCN A) stimulates the DNA synthesizing activities of the DNA polymerases, Pol I and Pol II, in this organism. Results: We have demonstrated that PfuPCNA interacts functionally with calf thymus DNA polymerase delta (Pol delta) and stimulates its activity. Moreo ver, human replication factor C (RFC) enhances the PfuPCNA-dependent DNA sy nthesis activity of Pol delta, indicating that human RFC works as the clamp loader for PfuPCNA. These results showed that the three-dimensional struct ures of archaral PCNA and RFC are actually similar enough to their eukaryot ic counterparts to allow a molecular substitution between the two biologica l domains, albeit at a lower efficiency. Conclusions: We found that the archaeal molecule interacts functionally wit h the eukaryotic members in the DNA replication process. This finding suppo rts the idea that studies on the DNA replication mechanism of archaeal orga nisms will provide many important clues for understanding of the intricate molecular recognition that is inherent to the DNA replication machinery in Eukarya.