Lethality of bypass polymerases in Escherichia coli cells with a defective clamp loader complex of DNA polymerase III

Mol Microbiol. 2003 Oct;50(1):193-204. doi: 10.1046/j.1365-2958.2003.03658.x.


Escherichia coli DNA polymerase III (Pol III) is one of the best studied replicative DNA polymerases. Here we report the properties of an E. coli mutant that lacks one of the subunits of the Pol III clamp loader complex, Psi (psi), as a result of the complete inactivation of the holD gene. We show that, in this mutant, chronic induction of the SOS response in a RecFOR-dependent way leads to lethality at high temperature. The SOS-induced proteins that are lethal in the holD mutant are the specialized DNA polymerases Pol II and Pol IV, combined with the division inhibitor SfiA. Prevention of SOS induction or inactivation of Pol II, Pol IV and SfiA encoding genes allows growth of the holD mutant, although at a reduced rate compared to a wild-type cell. In contrast, the SOS-induced Pol V DNA polymerase does not participate to the lethality of the holD mutant. We conclude that: (i) Psi is essential for efficient replication of the E. coli chromosome; (ii) SOS-induction of specialized DNA polymerases can be lethal in cells in which the replicative polymerase is defective, and (iii) specialized DNA polymerases differ in respect to their access to inactivated replication forks.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • DNA Polymerase III / genetics
  • DNA Polymerase III / metabolism*
  • DNA Replication / genetics
  • DNA Replication / physiology
  • 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 / physiology*
  • Escherichia coli Proteins / genetics*
  • Escherichia coli Proteins / metabolism
  • Gene Deletion
  • Genes, Bacterial
  • Hot Temperature
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism
  • Mutagenesis, Insertional
  • Mutation
  • Recombination, Genetic / physiology
  • SOS Response, Genetics / physiology
  • Ultraviolet Rays


  • Bacterial Proteins
  • DNA-Binding Proteins
  • DinB protein, E coli
  • Escherichia coli Proteins
  • Multienzyme Complexes
  • holD protein, E coli
  • polB protein, E coli
  • recF protein, E coli
  • sulA protein, E coli
  • recF protein, Bacteria
  • DNA Polymerase III
  • DNA polymerase V, E coli
  • DNA-Directed DNA Polymerase