title: Base-pairing preferences, physicochemical properties and mutational behaviour of the DNA lesion 8-nitroguanine.
abstract: 8-Nitro-2'-deoxyguanosine (8-nitrodG) is a relatively unstable, mutagenic lesion of DNA that is increasingly believed to be associated with tissue inflammation. Due to the lability of the glycosidic bond, 8-nitrodG cannot be incorporated into oligodeoxynucleotides (ODNs) by chemical DNA synthesis and thus very little is known about its physicochemical properties and base-pairing preferences. Here we describe the synthesis of 8-nitro-2'-O-methylguanosine, a ribonucleoside analogue of this lesion, which is sufficiently stable to be incorporated into ODNs. Physicochemical studies demonstrated that 8-nitro-2'-O-methylguanosine adopts a syn conformation about the glycosidic bond; thermal melting studies and molecular modelling suggest a relatively stable syn-8-nitroG·anti-G base pair. Interestingly, when this lesion analogue was placed in a primer-template system, extension of the primer by either avian myeloblastosis virus reverse transcriptase (AMV-RT) or human DNA polymerase β (pol β), was significantly impaired, but where incorporation opposite 8-nitroguanine did occur, pol β showed a 2:1 preference to insert dA over dC, while AMV-RT incorporated predominantly dC. The fact that no 8-nitroG·G base pairing is seen in the primer extension products suggests that the polymerases may discriminate against this pairing system on the basis of its poor geometric match to a Watson-Crick pair.
authors.affiliation: Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, UK.
authors.forename: Inder
authors.initials: I
authors.lastname: Bhamra
authors.forename: Patricia
authors.initials: P
authors.lastname: Compagnone-Post
authors.forename: Ian A
authors.initials: IA
authors.lastname: O'Neil
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Iwanejko
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Bates
authors.forename: Richard
authors.initials: R
authors.lastname: Cosstick
mesh_terms: D020029:Base Pairing; D004247:DNA / Q000096:biosynthesis; D004249:DNA Damage; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry; D006151:Guanosine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D006868:Hydrolysis; D016296:Mutagenesis; D009154:Mutation; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000737:chemistry; D013698:Templates, Genetic
chemical_list: C577843:8-nitro-2'-O-methylguanosine; C095838:8-nitroguanine; D009838:Oligodeoxyribonucleotides; D006151:Guanosine; D006147:Guanine; D004247:DNA