RdgB acts to avoid chromosome fragmentation in Escherichia coli.
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.
Bradshaw
Jill S
JS
Department of Microbiology, University of Illinois at Urbana-Champaign, B103 C&LSL, 601 South Goodwin Ave., 61801-3709, USA.
Kuzminov
Andrei
A
D002876:Chromosomes, Bacterial / Q000235:genetics*; D004249:DNA Damage; D004260:DNA Repair; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000235:genetics / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D011755:Pyrophosphatases / Q000235:genetics / Q000378:metabolism*
D029968:Escherichia coli Proteins; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; D043211:Exodeoxyribonuclease V; C468322:exodeoxyribonuclease V, E coli; D043224:Deoxyribonuclease (Pyrimidine Dimer); D011755:Pyrophosphatases; C474645:RdgB protein, E coli