title: Excision of damaged thymine residues from gamma-irradiated poly(dA-dT) by crude extracts of Escherichia coli.
abstract: Crude extracts of E. coli endo I(-) and E. coli endo I(-)uvrA6(-) possess the ability to remove thymine products of the 5,6-dihydroxy-dihydrothymine type from gamma-irradiated or osmium tetroxide-oxidized poly(dA-dT). It is shown that the uvrA-gene product, which is responsible for incision close to photodimers in prereplication ultraviolet repair in E. coli, is not required for, but may aid in, the excision of gamma-ray products of the 5,6-dihydroxy-dihydrothymine type. Ring-damaged thymine products are also removed by E. coli extracts from osmium tetroxide-oxidized poly(dA-dT), which contains only 5,6-dihydroxy-dihydrothymine but no strand breakage, indicating that product excision occurs in the absence of radiation-induced breaks. On the average, 8 to 16 nucleotides are removed from the polymer per ring-damaged thymine residue excised by extracts from both strains and for gamma-irradiated and osmium tetroxide-oxidized polymer.
mesh_terms: D000227:Adenine Nucleotides / Q000378:metabolism* / Q000528:radiation effects; D001665:Binding Sites; D002848:Chromatography, DEAE-Cellulose; D004260:DNA Repair; D004720:Endonucleases / Q000494:pharmacology*; D004926:Escherichia coli / Q000201:enzymology; D005720:Gamma Rays; D009992:Osmium / Q000494:pharmacology; D011119:Polynucleotides / Q000378:metabolism* / Q000528:radiation effects; D014176:Protein Biosynthesis; D011830:Radiation Effects; D013941:Thymine / Q000032:analysis / Q000378:metabolism*; D013942:Thymine Nucleotides / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D000227:Adenine Nucleotides; D011119:Polynucleotides; D013942:Thymine Nucleotides; D009992:Osmium; D004720:Endonucleases; D013941:Thymine