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A Human Endonuclease Incises Ultraviolet‐Irradiated DNA at Cytosines and Oxidized DNA at Thymines
Author(s) -
Gallagher Patricia E.,
Weiss Randi B.,
Brent Thomas P.,
Duker Nahum J.
Publication year - 1989
Publication title -
molecular carcinogenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.254
H-Index - 97
eISSN - 1098-2744
pISSN - 0899-1987
DOI - 10.1002/mc.2940020404
Subject(s) - thymine , dna , cytosine , pyrimidine dimer , biology , endonuclease , biochemistry , pyrimidine , dna glycosylase , microbiology and biotechnology , enzyme , dna damage
Both ultraviolet irradiation and oxidation of DNA produce a variety of pyrimidine base damages. A human endonuclease recognizes such altered bases on these DNA substrates. This human endonuclease incises ultraviolet‐irradiated DNA exclusively at sites of photochemically modified cytosines. The precise sites of incision by the human enzyme were determined by DNA sequencing. Chemically oxidized DNA was incised exclusively at thymine loci. The degree of enzymic cleavage at cytosine photoproducts was identical at each site. However, the extent of incision at selected oxidized thymine residues varied within the DNA sequence. These results indicate that the distribution of thymine oxidative modifications is influenced by the neighboring DNA bases.