Enzymatic recognition of DNA modifications induced by singlet oxygen and photosensitizers.
DNA modifications induced either by photosensitization (illumination in the presence of methylene blue) or by chemically generated singlet oxygen (thermal decomposition of an 1,4-etheno-2,3-benzodioxin) are recognized and incised by repair endonucleases present in crude bacterial cell extracts. Only a small fraction of the incised modifications are sites of base loss (AP-sites) sensitive to exonuclease III, endonuclease IV from E. coli or to the UV-endonuclease from M. luteus. Cell extracts from E. coli strains overproducing or defective in endonuclease III recognize the modifications induced by illumination in the presence of methylene blue just as well as do those from wild-type E. coli strains. This indicates that dihydropyrimidine derivatives, which are characteristic of hydroxyl radical-induced DNA modifications, are absent. In contrast, most of the modifications induced are not recognized by a cell extract from a fpg strain defective in formamidopyrimidine-DNA glycosylase FPG protein). Furthermore, incision by a cell extract from an E. coli strain overproducing FPG protein takes place at much lower protein concentration than with the wild-type strain. Experiments with purified FPG protein confirm that this enzyme is responsible for the recognition of singlet oxygen-induced DNA base modifications.
Institute of Pharmacology and Toxicology, University of Würzburg, FRG.
E
E
Müller
S
S
Boiteux
R P
RP
Cunningham
B
B
Epe
D003090:Coliphages / Q000235:genetics; D004279:DNA, Viral / Q000187:drug effects*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043382:DNA-Formamidopyrimidine Glycosylase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins; D005090:Exodeoxyribonucleases / Q000378:metabolism*; D007700:Kinetics; D008837:Micrococcus / Q000201:enzymology; D009097:Multienzyme Complexes / Q000378:metabolism*; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D010100:Oxygen / Q000494:pharmacology*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D026082:Singlet Oxygen; D013379:Substrate Specificity
D004279:DNA, Viral; D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; D011838:Radiation-Sensitizing Agents; D026082:Singlet Oxygen; C032219:UV endonuclease; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III; D043223:Deoxyribonuclease IV (Phage T4-Induced); C468972:endonuclease IV, E coli; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D010100:Oxygen