Low levels of endogenous oxidative damage cluster levels in unirradiated viral and human DNAs.
Ionizing radiation induces bistranded DNA damage clusters-two or more oxidized bases, abasic, sites or strand breaks on opposing strands within a few helical turns-but it is not known if clusters are also formed in unirradiated DNA in solution or in unirradiated cultured human cells. The frequencies of endogenous oxidized purine clusters (recognized by Escherichia coli Fpg protein), oxidized pyrimidine clusters (recognized by Nth protein), and abasic clusters (cleavage by Nfo protein) were determined using quantitative gel electrophoresis, electronic imaging, and number average length analysis. Methods of DNA isolation and storage were found to affect cluster levels significantly. In bacteriophage T7 DNA prepared using stringent conditions, the frequencies of these clusters were <1/Mbp. In DNA from unirradiated human 28SC monocytes, the levels of such clusters were, at most, a few per gigabase pair.
Sutherland
Betsy M
BM
Biology Department, Brookhaven National Laboratory, Upton NY 11973-5000, USA. bms@bnl.gov
Bennett
Paula V
PV
Cintron
Nela S
NS
Guida
Peter
P
Laval
Jacques
J
D001080:Apurinic Acid / Q000528:radiation effects*; D017123:Bacteriophage T7 / Q000235:genetics; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D004279:DNA, Viral / Q000528:radiation effects*; D043382:DNA-Formamidopyrimidine Glycosylase / Q000378:metabolism; D043224:Deoxyribonuclease (Pyrimidine Dimer) / Q000378:metabolism; D043223:Deoxyribonuclease IV (Phage T4-Induced) / Q000378:metabolism; D004587:Electrophoresis, Agar Gel; D004926:Escherichia coli / Q000821:virology; D029968:Escherichia coli Proteins / Q000378:metabolism; D005720:Gamma Rays; D006801:Humans; D009000:Monocytes / Q000378:metabolism / Q000528:radiation effects; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000528:radiation effects*; D011687:Purines / Q000528:radiation effects*; D011743:Pyrimidines / Q000528:radiation effects*
D004279:DNA, Viral; D029968:Escherichia coli Proteins; D011687:Purines; D011743:Pyrimidines; D001080:Apurinic Acid; D004247:DNA; D043223:Deoxyribonuclease IV (Phage T4-Induced); C468972:endonuclease IV, E coli; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli