Replisome fate upon encountering a leading strand block and clearance from DNA by recombination proteins

J Biol Chem. 2007 Aug 31;282(35):25903-16. doi: 10.1074/jbc.M703777200. Epub 2007 Jul 2.


Replication forks that collapse upon encountering a leading strand lesion are reactivated by a recombinative repair process called replication restart. Using rolling circle DNA substrates to model replication forks, we examine the fate of the helicase and both DNA polymerases when the leading strand polymerase is blocked. We find that the helicase continues over 0.5 kb but less than 3 kb and that the lagging strand DNA polymerase remains active despite its connection to a stalled leading strand enzyme. Furthermore, the blocked leading strand polymerase remains stably bound to the replication fork, implying that it must be dismantled from DNA in order for replication restart to initiate. Genetic studies have identified at least four gene products required for replication restart, RecF, RecO, RecR, and RecA. We find here that these proteins displace a stalled polymerase at a DNA template lesion. Implications of these results for replication fork collapse and recovery are discussed.

Publication types

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

MeSH terms

  • Cell-Free System
  • DNA / chemistry
  • DNA / metabolism
  • DNA Polymerase III / chemistry*
  • DNA Polymerase III / metabolism
  • DNA Replication / physiology*
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / metabolism
  • Plasmids / chemistry*
  • Plasmids / metabolism
  • Recombinases / chemistry*
  • Recombinases / metabolism
  • Recombination, Genetic / physiology*


  • Escherichia coli Proteins
  • Recombinases
  • DNA
  • DNA Polymerase III