Replication protein A in Pyrococcus furiosus is involved in homologous DNA recombination

Single-stranded DNA-binding protein in Bacteria and replication protein A (RPA) in Eukarya play crucial roles in DNA replication, repair, and recombination processes. We identified an RPA complex from the hyperthermophilic archaeon, Pyrococcus furiosus. Unlike the single-peptide RPAs from the methanogenic archaea, Methanococcus jannaschii and Methanothermobacter thermoautotrophicus, P. furiosus RPA (PfuRPA) exists as a stable hetero-oligomeric complex consisting of three subunits, RPA41, RPA14, and RPA32. The amino acid sequence of RPA41 has some similarity to those of the eukaryotic RPA70 subunit and the M. jannaschii RPA. On the other hand, RPA14 and RPA32 do not share homology with any known open reading frames from Bacteria and Eukarya. However, six of eight archaea, whose total genome sequences have been published, have the open reading frame homologous to RPA32. The PfuRPA complex, but not each subunit alone, specifically bound to a single-stranded DNA and clearly enhanced the efficiency of an in vitro strand-exchange reaction by the P. furiosus RadA protein. Moreover, immunoprecipitation analyses showed that PfuRPA interacts with the recombination proteins, RadA and Hjc, as well as replication proteins, DNA polymerases, primase, proliferating cell nuclear antigen, and replication factor C in P. furiosus cells. These results indicate that PfuRPA plays important roles in the homologous DNA recombination in P. furiosus.