The role of metal ion binding in generating 8-hydroxy-2 0 -deoxyguanosine from the nucleoside 2 0 -deoxyguanosine and the nucleotide 2 0 -deoxyguanosine-5 0 -monophosphate Scott D. Noblitt 1 , Amelia M. Huehls, Daniel L. Morris Jr. * Rose-Hulman Institute of Technology, Department of Chemistry, 5500 Wabash Avenue, Terre Haute, IN 47803, United States Received 17 August 2006; received in revised form 21 November 2006; accepted 22 November 2006 Available online 30 November 2006 Abstract The metal ions Cu(II), Fe(II), and Cr(III) were allowed to react with H 2 O 2 in the presence of either the mononucleoside 2 0 -deoxy- guanosine (dG) or the mononucleotide 2 0 -deoxyguanosine-5 0 -monophosphate (dGMP). The percentage of reacted dG or dGMP that formed the oxidative damage marker 8-hydroxy-2 0 -deoxyguanosine (8-OH-dG) was monitored. Oxidative damage from reactions involv- ing Cu(II) appear dependent on an interaction between copper and N7 on the guanine base. Any interactions involving the phosphate group have little additional effect on overall oxidative damage or 8-OH-dG production. Reactions involving Fe(II) seem very dependent on an interaction that may involve both N7 on the guanine base and the phosphate group. This interaction may slow oxidation of Fe(II) to Fe(III) in solution, keeping iron in a readily available form to undergo the Fenton reaction. Chromium(III) appears to interact with the phosphate group of dGMP, resulting in significant overall oxidative damage. However, production of 8-OH-dG appears to be very dependent on the ability of Cr(III) to interact with N7 on the guanine base, an interaction that seems to be weak for both the mono- nucleoside and mononucleotide. Ó 2006 Elsevier Inc. All rights reserved. Keywords: Nucleoside; Nucleotide; Metal ion binding; 8-Hydroxy-2 0 -deoxyguanosine 1. Introduction Many transition metal ions undergo reactions with H 2 O 2 to produce reactive oxygen species (ROS) that give rise to damage associated with many diseases, clinical con- ditions and aging [1–16]. While specific ROS produced may depend on reaction conditions [17,18], Fe(II) is generally believed to react with H 2 O 2 to produce Fe(III) and Å OH (Fenton reaction) [19]. Other metal ions that generate ROS in the presence of H 2 O 2 often do so through a ‘‘Fen- ton-like’’ reaction in which the metal ion is oxidized. For instance, the behavior of Cr(III) closely mimics that of Fe(II) in that it appears to be oxidized directly by H 2 O 2 to form Cr(IV) and Å OH [20–24]. Oxidative DNA damage is very site-specific, targeting the readily oxidized guanine base and forming the hydrox- ylated derivative 8-hydroxy-2 0 -deoxyguanosine (8-OH-dG) [1–6,25–27]. A review of oxidative base damage leading to DNA strand scission is provided by Burrows and Muller [28]. The metal ions Cu(II), Fe(II) and Cr(III) are among several that exhibit site-specific damage to the guanine base in DNA, resulting in double-strand breaks and production of 8-OH-dG [29,30]. Iron(II) has also been shown to pro- duce 8-OH-dG from RNA [31]. Metal ions may associate with the phosphate groups on the DNA backbone or with individual bases or base pairs within an intact DNA helix [32]. The relative levels of double and single strand breaks and production of bulky oxidative DNA lesions differ sig- nificantly with metal ion identity, indicating that metal ions 0162-0134/$ - see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.jinorgbio.2006.11.014 * Corresponding author. Tel.: +1 812 877 8314; fax: +1 812 872 6019. E-mail address: daniel.morris@rose-hulman.edu (D.L. Morris Jr.). 1 Present address: Chemistry Department, Colorado State University, Ft. Collins, CO 80523, United States. www.elsevier.com/locate/jinorgbio Journal of Inorganic Biochemistry 101 (2007) 536–542 JOURNAL OF Inorganic Biochemistry