title: DnaA protein interacts with RNA polymerase and partially protects it from the effect of rifampicin.
abstract: The Escherichia coli DnaA protein forms an oligomer at the origin and initiates chromosome replication with the aid of architectural elements and transcription by RNA polymerase. Rifampicin inhibits initiation of transcription by RNA polymerase and thus also initiation of replication. Here, we report that wild-type cells undergo rifampicin-resistant initiation of replication during slow growth in acetate medium. The rifampicin-resistant initiation was prevented by reducing the availability of DnaA. In vitro experiments showed that the DnaA protein interacted with RNA polymerase and that it afforded a partial protection from the negative effect of rifampicin. It is possible that rifampicin-resistant rounds of replication occur when a surplus of DnaA is available at the origin. In rich medium wild-type cells do not exhibit rifampicin-resistant rounds of replication, possibly indicating that there is no surplus DnaA, and that DnaA activity is the factor limiting the process of initiation. During growth in acetate medium, on the contrary, DnaA activity is not limiting in the same way because an initiation potential is present and can be turned into extra rounds of replication when rifampicin is added. The result suggests that regulation of replication initiation may differ at different growth rates.
authors.affiliation: Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Rikshospitalet, University of Oslo, 0310 Oslo, Norway.
authors.forename: Ingvild
authors.initials: I
authors.lastname: Flåtten
authors.lastname: Morigen
authors.forename: Kirsten
authors.initials: K
authors.lastname: Skarstad
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D001426:Bacterial Proteins / Q000032:analysis / Q000378:metabolism*; D003470:Culture Media; D004261:DNA Replication / Q000187:drug effects; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000032:analysis / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D012293:Rifampin / Q000494:pharmacology*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D029968:Escherichia coli Proteins; D012321:DNA-Directed RNA Polymerases; D019342:Acetic Acid; D012293:Rifampin