INITIATION AND TERMINATION OF DNA REPLICATION OF PLASMID pKYM VIA A ROLLING-CIRCLE MECHANISM

The replication origin of plasmid pKYM, which replicates via a rolling-circle mechanism, is composed of three regions with the following characteristics. 1) The core origin, which is essential for initiation of DNA replication, consists of 39-base pairs. The purified Rep protein of pKYM (RepK) binds specifically to this 39-base-pair region. Within the 39 base-pair origin, there is a sequence of 22 base pairs that is sufficient for termination. 2) The initiation-enhancing region consists of a 98-base-pair-region downstream of the core origin. A host protein(s) binds to this region in the presence of RepK. 3) A 34-base-pair sequence upstream of the core origin is essential for the multiplication of pKYM. Multimers of the plasmid DNA were produced in the absence of this region. The region may enhance correct processing of the unit length plasmid DNA. A host protein binds to this region.