RdgB acts to avoid chromosome fragmentation in Escherichia coli

Mol Microbiol. 2003 Jun;48(6):1711-25. doi: 10.1046/j.1365-2958.2003.03540.x.

Abstract

Bacterial RecA protein is required for repair of two-strand DNA lesions that disable whole chromosomes. recA mutants are viable, suggesting a considerable cellular capacity to avoid these chromosome-disabling lesions. recA-dependent mutants reveal chromosomal lesion avoidance pathways. Here we characterize one such mutant, rdgB/yggV, deficient in a putative inosine/xanthosine triphosphatase, conserved throughout kingdoms of life. The rdgB recA lethality is suppressed by inactivation of endonuclease V (gpnfi) specific for DNA-hypoxanthines/xanthines, suggesting that RdgB either intercepts improper DNA precursors dITP/dXTP or works downstream of EndoV in excision repair of incorporated hypoxathines/xanthines. We find that DNA isolated from rdgB mutants contains EndoV-recognizable modifications, whereas DNA from nfi mutants does not, substantiating the dITP/dXTP interception by RdgB. rdgB recBC cells are inviable, whereas rdgB recF cells are healthy, suggesting that chromosomes in rdgB mutants suffer double-strand breaks. Chromosomal fragmentation is indeed observed in rdgB recBC mutants and is suppressed in rdgB recBC nfi mutants. Thus, one way to avoid chromosomal lesions is to prevent hypoxanthine/xanthine incorporation into DNA via interception of dITP/dXTP.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Chromosomes, Bacterial / genetics*
  • DNA Damage*
  • DNA Repair*
  • Deoxyribonuclease (Pyrimidine Dimer)
  • Endodeoxyribonucleases / genetics
  • Endodeoxyribonucleases / metabolism
  • Escherichia coli / genetics*
  • Escherichia coli / growth & development
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Exodeoxyribonuclease V
  • Exodeoxyribonucleases / genetics
  • Exodeoxyribonucleases / metabolism
  • Mutagenesis, Insertional
  • Mutation
  • Plasmids / genetics
  • Pyrophosphatases / genetics
  • Pyrophosphatases / metabolism*

Substances

  • Escherichia coli Proteins
  • Endodeoxyribonucleases
  • Exodeoxyribonucleases
  • Exodeoxyribonuclease V
  • exodeoxyribonuclease V, E coli
  • Deoxyribonuclease (Pyrimidine Dimer)
  • Pyrophosphatases
  • RdgB protein, E coli