title: Hidden in plain sight: subtle effects of the 8-oxoguanine lesion on the structure, dynamics, and thermodynamics of a 15-base pair oligodeoxynucleotide duplex.
abstract: The base lesion 8-oxoguanine is formed readily by oxidation of DNA, potentially leading to G → T transversion mutations. Despite the apparent similarity of 8-oxoguanine-cytosine base pairs to normal guanine-cytosine base pairs, cellular base excision repair systems effectively recognize the lesion base. Here we apply several techniques to examine a single 8-oxoguanine lesion at the center of a nonpalindromic 15-mer duplex oligonucleotide in an effort to determine what, if anything, distinguishes an 8-oxoguanine-cytosine (8oxoG-C) base pair from a normal base pair. The lesion duplex is globally almost indistinguishable from the unmodified parent duplex using circular dichroism spectroscopy and ultraviolet melting thermodynamics. The DNA mismatch-detecting photocleavage agent Rh(bpy)(2)chrysi(3+) cleaves only weakly and nonspecifically, revealing that the 8oxoG-C pair is locally stable at the level of the individual base pairs. Nuclear magnetic resonance spectra are also consistent with a well-conserved B-form duplex structure. In the two-dimensional nuclear Overhauser effect spectra, base-sugar and imino-imino cross-peaks are strikingly similar between parent and lesion duplexes. Changes in chemical shift due to the 8oxoG lesion are localized to its complementary cytosine and to the 2-3 bp immediately flanking the lesion on the lesion strand. Residues further removed from the lesion are shown to be unperturbed by its presence. Notably, imino exchange experiments indicate that the 8-oxoguanine-cytosine pair is strong and stable, with an apparent equilibrium constant for opening equal to that of other internal guanine-cytosine base pairs, on the order of 10(-6). This collection of experiments shows that the 8-oxoguanine-cytosine base pair is incredibly stable and similar to the native pair.
authors: Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, United States.
authors: Charisse M
authors: CM
authors: Crenshaw
authors: Jacqueline E
authors: JE
authors: Wade
authors: Haribabu
authors: H
authors: Arthanari
authors: Dominique
authors: D
authors: Frueh
authors: Benjamin F
authors: BF
authors: Lane
authors: Megan E
authors: ME
authors: Núñez
mesh_terms: D020029:Base Pairing; D001483:Base Sequence; D004249:DNA Damage / Q000187:drug effects; D004260:DNA Repair; D006147:Guanine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D009838:Oligodeoxyribonucleotides; C024829:8-hydroxyguanine; D006147:Guanine