A hand-off mechanism for primosome assembly in replication restart

Mol Cell. 2007 Jun 22;26(6):781-93. doi: 10.1016/j.molcel.2007.05.012.


Collapsed DNA replication forks must be reactivated through origin-independent reloading of the replication machinery (replisome) to ensure complete duplication of cellular genomes. In E. coli, the PriA-dependent pathway is the major replication restart mechanism and requires primosome proteins PriA, PriB, and DnaT for replisome reloading. However, the molecular mechanisms that regulate origin-independent replisome loading are not fully understood. Here, we demonstrate that assembly of primosome protein complexes represents a key regulatory mechanism, as inherently weak PriA-PriB and PriB-DnaT interactions are strongly stimulated by single-stranded DNA. Furthermore, the binding site on PriB for single-stranded DNA partially overlaps the binding sites for PriA and DnaT, suggesting a dynamic primosome assembly process in which single-stranded DNA is handed off from one primosome protein to another as a repaired replication fork is reactivated. This model helps explain how origin-independent initiation of DNA replication is restricted to repaired replication forks, preventing overreplication of the genome.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites / physiology
  • DNA Helicases / genetics
  • DNA Helicases / metabolism*
  • DNA Replication / physiology*
  • DNA, Bacterial / genetics
  • DNA, Bacterial / metabolism
  • DNA, Single-Stranded / genetics
  • DNA, Single-Stranded / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • DNA-Directed DNA Polymerase / genetics
  • DNA-Directed DNA Polymerase / metabolism*
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Genome, Bacterial / physiology
  • Models, Biological*
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism*
  • Protein Binding / physiology
  • Replication Origin


  • DNA, Bacterial
  • DNA, Single-Stranded
  • DNA-Binding Proteins
  • DnaT protein, E coli
  • Escherichia coli Proteins
  • Multienzyme Complexes
  • PriB protein, E coli
  • DNA synthesome
  • DNA-Directed DNA Polymerase
  • priA protein, E coli
  • DNA Helicases

Associated data

  • PDB/2PNH