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Updated: Jul 19, 2026

Determination of the Optimal Chromosomal Location(s) for a DNA Element in Escherichia coli Using a Novel Transposon-mediated Approach
Published on: September 11, 2017
IHF-dependent activation of P1 plasmid origin by dnaA
Richard A Fekete1, Tatiana Venkova-Canova, Kyusung Park
1Laboratory of Biochemistry, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892-4255, USA.
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.
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