title: SeqA blocking of DnaA-oriC interactions ensures staged assembly of the E. coli pre-RC.
abstract: DnaA occupies only the three highest-affinity binding sites in E. coli oriC throughout most of the cell cycle. Immediately prior to initiation of chromosome replication, DnaA interacts with additional recognition sites, resulting in localized DNA-strand separation. These two DnaA-oriC complexes formed during the cell cycle are functionally and temporally analogous to yeast ORC and pre-RC. After initiation, SeqA binds to hemimethylated oriC, sequestering oriC while levels of active DnaA are reduced, preventing reinitiation. In this paper, we investigate how resetting of oriC to the ORC-like complex is coordinated with SeqA-mediated sequestration. We report that oriC resets to ORC during sequestration. This was possible because SeqA blocked DnaA binding to hemimethylated oriC only at low-affinity recognition sites associated with GATC but did not interfere with occupation of higher-affinity sites. Thus, during the sequestration period, SeqA repressed pre-RC assembly while ensuring resetting of E. coli ORC.
authors.affiliation: Department of Biological Sciences, Florida Institute of Technology, 150 West University Boulevard, Melbourne, Florida 32901 USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Nievera
authors.forename: Julien J-C
authors.initials: JJ
authors.lastname: Torgue
authors.forename: Julia E
authors.initials: JE
authors.lastname: Grimwade
authors.forename: Alan C
authors.initials: AC
authors.lastname: Leonard
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D018983:DNA Footprinting; D019175:DNA Methylation; D004261:DNA Replication / Q000502:physiology; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology*; D046911:Macromolecular Substances / Q000378:metabolism; D008969:Molecular Sequence Data; D051738:Origin Recognition Complex / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D029968:Escherichia coli Proteins; D046911:Macromolecular Substances; C114650:OriC chromosomal replication origin; D051738:Origin Recognition Complex; C089746:SeqA protein, E coli