title: IHF-dependent activation of P1 plasmid origin by dnaA.
abstract: In bacteria, many DNA-protein interactions that initiate transcription, replication and recombination require the mediation of DNA architectural proteins such as IHF and HU. For replication initiation, plasmid P1 requires three origin binding proteins: the architectural protein HU, a plasmid-specific initiator, RepA, and the Escherichia coli chromosomal initiator, DnaA. The two initiators bind in the origin of replication to multiple sites, called iterons and DnaA boxes respectively. We show here that all five known DnaA boxes can be deleted from the plasmid origin provided the origin is extended by about 120 bp. The additional DNA provides an IHF site and most likely a weak DnaA binding site, because replacing the putative site with an authentic DnaA box enhanced plasmid replication in an IHF-dependent manner. IHF most likely brings about interactions between distally bound DnaA and RepA by bending the intervening DNA. The role of IHF in activating P1 origin by allowing DnaA binding to a weak site is reminiscent of the role the protein plays in initiating the host chromosomal replication.
authors.affiliation: Laboratory of Biochemistry, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892-4255, USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Fekete
authors.forename: Tatiana
authors.initials: T
authors.lastname: Venkova-Canova
authors.forename: Kyusung
authors.initials: K
authors.lastname: Park
authors.forename: Dhruba K
authors.initials: DK
authors.lastname: Chattoraj
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D004261:DNA Replication / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D034982:Integration Host Factors / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics*; D011485:Protein Binding; D018741:Replication Origin / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D034982:Integration Host Factors; D015534:Trans-Activators