COMPLETE NUCLEOTIDE-SEQUENCE OF THE SULFOLOBUS-ISLANDICUS MULTICOPY PLASMID PRN1

The complete sequence of the 5350-bp plasmid pRN1 from the crenarchaeo te Sulfolobus islandicus has been determined. This plasmid is the firs t to be sequenced from this group of thermoacidophilic archaebacteria (Archaea) and its high copy number and wide host range make it a good candidate for a cloning vector. pRN1 contains several open reading fra mes, including one that spans over half the plasmid and has significan t similarity to the helicase domain of viral primase proteins. Directl y upstream of this putative primase is a homologue of Cop, a family of small proteins from promiscuous eubacterial plasmids which control co py number by repressing the expression of the replication initiation p rotein. In eubacterial plasmids cop is found upstream of the replicati on initiator protein, The location of a cop homologue upstream of a pr imase-like gene in pRN1 suggests that it controls DNA replication in a manner similar to these eubacterial plasmids, but does so using a mix ture of componants from plasmids and viruses. (C) 1996 Academic Press, Inc,