title: Inhibition of enzymic incision of thymine dimers by covalently bound 2-[N-[(deoxyguanosin-8-yl)acetyl]amino]fluorene in deoxyribonucleic acid.
abstract: The effects of DNA adducts of the carcinogen 2-[N-(acetoxyacetyl)amino]fluorene on enzymic incision of thymine dimers was investigated. Escherichia coli DNA labeled with [3H]thymidine was reacted with the carcinogen. Thymine dimers were then introduced into the modified DNA by irradiation with monochromatic 254-nm light in the presence of the photosensitizer silver nitrate. This DNA containing both types of damages, mainly 2-[N-[(deoxyguanosin-8-yl)acetyl]fluorene and thymine dimers, was then used as substrate for pyrimidine dimer-DNA glycosylase, purified from E. coli infected by bacteriophage T4. Activity was assayed by measuring release of free labeled thymine after photoreversal of the enzyme-reacted DNA by 254-nm light. The Vmax of the enzyme was decreased when it was reacted with the extensively arylamidated substrate. This inhibition of incision of pyrimidine dimers was increased with the number of carcinogen-DNA adducts, although no enzymic activity against modified guanines was present. Therefore, carcinogen-modified purine moieties can interfere with initiation of excision repair of ultraviolet-induced pyrimidine dimers. This suggests an indirect pathway by which modified DNA bases can be mutagenic.
mesh_terms: D015073:2-Acetylaminofluorene / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000633:toxicity*; D004247:DNA / Q000528:radiation effects; D045647:DNA Glycosylases; D004260:DNA Repair; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009699:N-Glycosyl Hydrolases / Q000037:antagonists & inhibitors*; D011740:Pyrimidine Dimers / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D011740:Pyrimidine Dimers; C018776:N-(deoxyguanosin-8-yl)acetylaminofluorene; D004247:DNA; D015073:2-Acetylaminofluorene; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C036401:deoxyribopyrimidine endonucleosidase; D003849:Deoxyguanosine