SOS-dependent A-->G transitions induced by hydroxyl radical generating system hypoxanthine/xanthine oxidase/Fe3+/EDTA are accompanied by the increase of Fapy-adenine content in M13 mp18 phage DNA.
Gas chromatography/isotope dilution-mass spectrometry with selected ion monitoring (GC/IDMS-SIM) was used to measure oxidised bases in hypoxanthine/xanthine oxidase/Fe3+/EDTA modified ss M13 mp18 phage DNA. A dose-dependent increase of oxidised bases content in DNA was observed with the biggest augmentation of FapyGua, thymine glycol and FapyAde. The amount of 8-OH-Gua was relatively high both in non-oxidised and oxidised DNA, and increased to the same extent as FapyAde and ThyGly. DNA oxidation caused a dramatic decrease in phage survival after transfection to E. coli. Survival was improved 2.8-fold after induction of the SOS system by UV irradiation of bacteria and mutation frequency of the lacZ gene in SOS conditions increased 7-fold over that in non-irradiated bacteria. Spectrum of mutations was different from those reported previously and mutations were distributed rather randomly within M13 lacZ sequence, which was in contrast to previous findings, where with non-chelated metal ions other types of mutations were found in several clusters. Thus, conditions of DNA oxidation and accessibility of metal ions for DNA bases might be important factors for generating different DNA damages and mutations. Major base substitutions found both in SOS-induced and non-induced E. coli but with higher mutation frequency in SOS-induced cells were C-->A (approximately 20-fold increase in SOS-conditions), G-->A (9-fold increase) and G-->C (4.5-fold increase). Very few G-->T transitions were found. A particularly large group of A-->G transitions appeared only in SOS-induced bacteria and was accompanied by augmentation of FapyAde content in the phage DNA with undetectable 2-OH-Ade. It is then possible that imidazole ring-opened adenine mimics guanine during DNA replication and pairs with cytosine yielding A-->G transitions in SOS-induced bacteria.
Graziewicz
M A
MA
Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.
Zastawny
T H
TH
Oliński
R
R
Tudek
B
B
D017104:Bacteriophage M13 / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D001483:Base Sequence; D004249:DNA Damage; D004277:DNA, Single-Stranded / Q000187:drug effects / Q000235:genetics; D004279:DNA, Viral / Q000187:drug effects* / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D005290:Ferric Compounds / Q000494:pharmacology; D005814:Genes, Viral / Q000235:genetics; D017665:Hydroxyl Radical / Q000009:adverse effects* / Q000378:metabolism; D019271:Hypoxanthine / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D018384:Oxidative Stress; D017354:Point Mutation; D011743:Pyrimidines / Q000737:chemistry / Q000378:metabolism*; D013014:SOS Response, Genetics / Q000502:physiology*; D014969:Xanthine Oxidase / Q000378:metabolism
D004277:DNA, Single-Stranded; D004279:DNA, Viral; D005290:Ferric Compounds; D011743:Pyrimidines; D019271:Hypoxanthine; D017665:Hydroxyl Radical; C039544:4,6-diamino-5-N-formamidopyrimidine; D004492:Edetic Acid; D014969:Xanthine Oxidase