title: Formation of modified cleavage termini from the reaction of chromium(V) with DNA.
abstract: Reaction of a 25 bp oligonucleotide with the high valent chromium complex, bis(2-ethyl-2-hydroxybutyrato)oxochromate(V) (Cr(V)-EHBA) produced both Frank- and alkali-labile strand breaks that were sequence-neutral. Frank strand break formation was found to be O2-dependent while formation of alkali-labile strand breaks were O2-independent. Reaction of Cr(V)-EHBA with the 5'-32P-labeled oligomer under oxygenated conditions formed the modified 3'-terminus, 3'-phosphoglycolate, as well as the 3'-phosphate terminus. Formation of the 3'-phosphoglycolate termini, and the O2 dependence of the reactions were consistent with a mechanism involving abstraction of the C4' hydrogen atom from the deoxyribose moiety of DNA. Identical reactions using the 3'-32P-labeled oligomer yielded only 5'-phosphate termini as assigned by co-migration with Maxam-Gilbert markers. Analogous cleavage profiles and modified termini were observed for the reaction of Cr(V)-EHBA and DNA in the presence of hydrogen peroxide. With the addition of hydrogen peroxide, the DNA cleavage reactions were O2-independent and the level of DNA cleavage was enhanced over that observed with Cr(V)-EHBA alone. These findings suggest an oxidation mechanism whereby a reductive intermediate of the carcinogen chromate, Cr(V), can cause DNA damage that mimics oxygen radical DNA damaging pathways.
authors.affiliation: University of Montana, Department of Chemistry, Missoula 59812, USA. sugden@selway.umt.edu
authors.forename: K D
authors.initials: KD
authors.lastname: Sugden
mesh_terms: D002273:Carcinogens / Q000378:metabolism*; D002857:Chromium / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D004249:DNA Damage; D004591:Electrophoresis, Polyacrylamide Gel; D006861:Hydrogen Peroxide / Q000378:metabolism; D066298:In Vitro Techniques; D009942:Organometallic Compounds / Q000378:metabolism*; D010084:Oxidation-Reduction
chemical_list: D002273:Carcinogens; D009942:Organometallic Compounds; D002857:Chromium; C083520:bis(2-hydroxy-2-ethylbutanoato)oxochromate(V); D004247:DNA; D006861:Hydrogen Peroxide