SeqA blocking of DnaA-oriC interactions ensures staged assembly of the E. coli pre-RC

Mol Cell. 2006 Nov 17;24(4):581-92. doi: 10.1016/j.molcel.2006.09.016.

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Bacterial Outer Membrane Proteins / physiology*
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • DNA Footprinting
  • DNA Methylation
  • DNA Replication / physiology
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / genetics
  • DNA, Bacterial / metabolism*
  • DNA-Binding Proteins / metabolism*
  • DNA-Binding Proteins / physiology*
  • Escherichia coli / genetics*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / physiology*
  • Macromolecular Substances / metabolism
  • Molecular Sequence Data
  • Origin Recognition Complex / genetics
  • Origin Recognition Complex / metabolism*
  • Protein Binding

Substances

  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • DNA, Bacterial
  • DNA-Binding Proteins
  • DnaA protein, Bacteria
  • Escherichia coli Proteins
  • Macromolecular Substances
  • OriC chromosomal replication origin
  • Origin Recognition Complex
  • SeqA protein, E coli