title: Effect of the CopB auxiliary replication control system on stability of maintenance of Par(+) plasmid R1.
abstract: Plasmid R1 is a low-copy-number plasmid that is present at a level of about four or five copies per average cell. The copy number is controlled posttranscriptionally at the level of synthesis of the rate-limiting initiator protein RepA. In addition to this, R1 has an auxiliary system that derepresses a second promoter at low copy numbers, leading to increased repA mRNA synthesis. This promoter is normally switched off by a constitutively synthesized plasmid-encoded repressor protein, CopB; in cells with low copy numbers, the concentration of CopB is low and the promoter is derepressed. Here we show that the rate of loss of a Par(+) derivative of the basic replicon of R1 increased about sevenfold when the cells contained a high concentration of the CopB protein formed from a compatible plasmid.
authors.affiliation: Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, S-751 24 Uppsala, Sweden.
authors.forename: Jan A
authors.initials: JA
authors.lastname: Olsson
authors.forename: Johan
authors.initials: J
authors.lastname: Paulsson
authors.forename: Kurt
authors.initials: K
authors.lastname: Nordström
mesh_terms: D004265:DNA Helicases; D004261:DNA Replication; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D018628:Gene Dosage; D015964:Gene Expression Regulation, Bacterial; D010957:Plasmids / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D011506:Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; C045264:replication initiator protein; D004265:DNA Helicases