The replication protein of the Sulfolobus islandicus plasmid pRN1

The thermoacidophile crenarchaeote Sulfolobus ssp. is one of the best-studied Archaea. Cryptic and conjugative plasmids as well as viruses have been described for this genus. For the majority of the genetic elements only the genome sequence and the basic characteristics were determined. In contrast the fusellovirus SSV1 and the cryptic plasmid pRN1, which is the smallest known genetic element of the crenarchaeota, have been studied in more detail. The three gene products of the plasmid pRN1 have been characterized biochemically. The replication protein of the plasmid, a multifunctional enzyme, has a novel domain, termed prim/pol domain. This domain constitutes the first member of the DNA polymerase family E. Based on the biochemical characterization of the gene products a model of how pRN1 is replicated in vivo is proposed.