Kinetic aspects of control of plasmid replication by antisense RNA

Plasmids are replicating DNA molecules that are present in defined numbers of copies per cell. They encode systems that control their replication such that given steady-state values for their copy numbers are maintained. This is a special type of control, since it requires the genome to measure its concentration continuously and adjust its rate of replication to parallel the rate of growth of the cell mass. In this review we discuss the quantitative kinetic properties of copy-number control of the R1 plasmid, in which the control device is an antisense RNA that controls the synthesis of a protein that is rate-limiting for replication of the plasmid.