title: Structure of the 1,N(2)-etheno-2'-deoxyguanosine lesion in the 3'-G(epsilon dG)T-5' sequence opposite a one-base deletion.
abstract: The structure of the 1,N(2)-ethenodeoxyguanosine lesion (1,N(2)-epsilondG) has been characterized in 5'-d(CGCATXGAATCC)-3'.5'-d(GGATTCATGCG)-3' (X = 1,N(2)-epsilondG), in which there is no dC opposite the lesion. This duplex (named the 1-BD duplex) models the product of translesion bypass of 1,N(2)-epsilondG by Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4) [Zang, H., Goodenough, A. K., Choi, J. Y., Irimia, A., Loukachevitch, L. V., Kozekov, I. D., Angel, K. C., Rizzo, C. J., Egli, M., and Guengerich, F. P. (2005) J. Biol. Chem. 280, 29750-29764], leading to a one-base deletion. The T(m) of this duplex is 6 degrees C higher than that of the duplex in which dC is present opposite the 1,N(2)-epsilondG lesion and 8 degrees C higher than that of the unmodified 1-BD duplex. Analysis of NOEs between the 1,N(2)-epsilondG imidazole and deoxyribose H1' protons and between the 1,N(2)-epsilondG etheno H6 and H7 protons and DNA protons establishes that 1,N(2)-epsilondG adopts the anti conformation about the glycosyl bond and that the etheno moiety is accommodated within the helix. The resonances of the 1,N(2)-epsilondG H6 and H7 etheno protons shift upfield relative to the monomer 1,N(2)-epsilondG, attributed to ring current shielding, consistent with their intrahelical location. NMR data reveal that Watson-Crick base pairing is maintained at both the 5' and 3' neighbor base pairs. The structure of the 1-BD duplex has been refined using molecular dynamics calculations restrained by NMR-derived distance and dihedral angle restraints. The increased stability of the 1,N(2)-epsilondG lesion in the absence of the complementary dC correlates with the one-base deletion extension product observed during the bypass of the 1,N(2)-epsilondG lesion by the Dpo4 polymerase, suggesting that stabilization of this bulged intermediate may be significant with regard to the biological processing of the lesion.
authors.affiliation: Department of Chemistry, Vanderbilt Institute of Chemical Biology, Center in MolecularToxicology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235, USA.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Shanmugam
authors.forename: Ivan D
authors.initials: ID
authors.lastname: Kozekov
authors.forename: F Peter
authors.initials: FP
authors.lastname: Guengerich
authors.forename: Carmelo J
authors.initials: CJ
authors.lastname: Rizzo
authors.forename: Michael P
authors.initials: MP
authors.lastname: Stone
mesh_terms: D001483:Base Sequence; D053801:Capillary Electrochromatography / Q000379:methods; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D018899:CpG Islands / Q000235:genetics*; D003432:Cross-Linking Reagents / Q000737:chemistry; D018360:Crystallography, X-Ray / Q000379:methods; D004247:DNA / Q000737:chemistry*; D004249:DNA Damage; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008967:Molecular Biology; D056004:Molecular Dynamics Simulation; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D010758:Phosphorus / Q000737:chemistry; D017384:Sequence Deletion
chemical_list: D003432:Cross-Linking Reagents; C054579:1,N(2)-ethenodeoxyguanosine; D010758:Phosphorus; D004247:DNA; D003849:Deoxyguanosine