title: Formation of intrastrand cross-link products between cytosine and adenine from UV irradiation of d((Br)CA) and duplex DNA containing a 5-bromocytosine.
abstract: Here, we showed that Pyrex-filtered UV light irradiation of d((Br)CA) gave rise to three types of intrastrand cross-link products, that is, d(C[5-N6]A), d(C[5-2]A), and d(C[5-8]A), where the C5 carbon atom of cytosine is covalently bonded to the N6 nitrogen atom, C2, and C8 carbon atoms of adenine, respectively. Furthermore, we demonstrated by LC-MS/MS that the UV irradiation of a 5-bromocytosine-containing duplex oligodeoxynucleotide (ODN) led to the formation of five cross-link products, that is, C[5-N6]A, C[5-2]A, C[5-8]A, A[2-5]C, and A[8-5]C, under both aerobic and anaerobic conditions. LC-MS/MS quantification results showed that the yields for the formation of these cross-link products are different. The presence of molecular oxygen reduces the yields for the formation of all cross-link products except A[2-5]C. To our knowledge, this is the first report about the formation of intrastrand cross-link products between cytosine and adenine in duplex DNA. The chemistry discovered here may facilitate the future preparations of oxidative cross-link lesion-bearing substrates for biochemical and biophysical studies.
authors.affiliation: Department of Chemistry and Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403, USA.
authors.forename: Haizheng
authors.initials: H
authors.lastname: Hong
authors.forename: Yinsheng
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000225:Adenine / Q000737:chemistry / Q000528:radiation effects; D003432:Cross-Linking Reagents / Q000737:chemistry / Q000528:radiation effects; D003596:Cytosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000528:radiation effects; D004247:DNA / Q000737:chemistry / Q000528:radiation effects; D004249:DNA Damage / Q000528:radiation effects; D005609:Free Radicals / Q000737:chemistry; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D005609:Free Radicals; C103182:5-bromocytosine; D003596:Cytosine; D004247:DNA; D000225:Adenine