Synthesis of a metallopeptide-PNA conjugate and its oxidative cross-linking to a DNA target.

A nickel(II)-PNA bioconjugate was prepared by formation of a salicylaldimine complex with the amino terminus of a peptide-PNA hybrid with the sequence Arg-His-Gly-[TACCTAGCAT]PNA-Arg-CONH2. Hybridization to complementary oligodeoxynucleotides was demonstrated, and covalent adduct formation was observed upon addition of KHSO5 as oxidant. In the absence of PNA, the reactivity of the phenolic radical generated as an intermediate was found to be G >> T >> C, A; by inclusion of the PNA delivery agent, cross-links between the two oligomers could be observed with T and C bases in the vicinity of the nickel complex, although G was still the most reactive site.

Effect of the oxidized guanosine lesions spiroiminodihydantoin and guanidinohydantoin on proofreading by Escherichia coli DNA polymerase I (Klenow fragment) in different sequence contexts.

Oxidative damage to DNA by endogenous and exogenous reactive oxygen species has been directly linked to cancer, aging, and a variety of neurological disorders. The potential mutagenicity of the primary guanine oxidation product 8-oxo-7,8-dihydroguanine (Og) has been studied intensively, and much information is available about its miscoding potential in vitro and in vivo. Recently, a variety of DNA lesions have been identified as oxidation products of both guanine and 8-oxoguanine, among them spiroiminodihydantoin (Sp) and guanidinohydantoin (Gh).

In vitro nucleotide misinsertion opposite the oxidized guanosine lesions spiroiminodihydantoin and guanidinohydantoin and DNA synthesis past the lesions using Escherichia coli DNA polymerase I (Klenow fragment).

The low redox potential of 8-oxo-7,8-dihydroguanine (OG), a molecule regarded as a marker of oxidative damage in cells, makes it an easy target for further oxidation. Using a temperature-dependent method of synthesis, the oxidation products of OG, guanidinohydantoin (Gh) and/or its isomer iminoallantoin (Ia) as well as spiroiminodihydantoin (Sp), have been site-specifically incorporated into DNA oligomers. Single nucleotide insertion and primer extension experiments using Escherichia coli Kf exo(-) DNA polymerase were carried out under "standing start" and "running start" conditions in various sequence contexts.

Structure and potential mutagenicity of new hydantoin products from guanosine and 8-oxo-7,8-dihydroguanine oxidation by transition metals.

In vitro work in this laboratory has identified new DNA lesions resulting from further oxidation of a common biomarker of oxidative damage, 8-oxo-7,8-dihydroguanine (OG). The major product of oxidation of OG in a nucleoside, nucleotide, or single-stranded oligodeoxynucleotide using metal ions that act as one-electron oxidants is the new nucleoside derivative spiroiminodihydantoin (Sp). In duplex DNA an equilibrating mixture of two isomeric products, guanidinohydantoin (Gh) and iminoallantoin (Ia), is produced.