Oxidative DNA Damage and Repair: Mechanisms, Mutations, and Relation to Diseases.

Oxidative DNA damage (ODD) by reactive oxygen species (ROS) or reactive nitrogen species (RNS) is an inevitable tradeoff for using oxidation processes by living cells as a source of energy [...

Sources of 2,5-diaminoimidazolone lesions in DNA damage initiated by hydroxyl radical attack.

The present study reports radiation-chemical yields of 2.5-diaminoimidazolone (Iz) derivatives in X-irradiated phosphate-buffered solutions of guanosine and double-stranded DNA. Various gassing conditions (air, N0/O (4:1), NO, vacuum) were employed to elucidate the contribution of several alternative pathways leading to Iz in reactions initiated by hydroxyl radical attack on guanine.

Association with Polyamines and Polypeptides Increases the Relative Yield of 2-Deoxyribonolactone Lesions in Radiation-Damaged DNA.

The production of 2-deoxyribonolactones (C1'-oxidation product), C4'-oxidized abasic sites and C5'-carbonyl terminated strand scission products was investigated in complexes of double-stranded DNA with protamine, poly-L-lysine and spermine exposed to X-ray radiation. The lesions were quantified by high-performance liquid chromatography through the release of the corresponding low-molecular-weight products 5-methylenefuran-2(5H)-one, N-(2'-hydroxy-ethyl)-5-methylene-D-pyrrolin-2-one and furfural, respectively. All binders were found to increase the relative yield of C1' oxidation up to 40% of the total 2-deoxyribose damage through the indirect effect versus approximately 18% typically found in homogeneous solutions by the same technique.

DNA damage by the sulfate radical anion: hydrogen abstraction from the sugar moiety versus one-electron oxidation of guanine.

The products of oxidative damage to double-stranded (ds) DNA initiated by photolytically generated sulfate radical anions SO4(•-) were analyzed using reverse-phase (RP) high-performance liquid chromatography (HPLC). Relative efficiencies of two major pathways were compared: production of 8-oxoguanine (8oxoG) and hydrogen abstraction from the DNA 2-deoxyribose moiety (dR) at C1,' C4,' and C5' positions. The formation of 8oxoG was found to account for 87% of all quantified lesions at low illumination doses.

Identification of the C4'-oxidized abasic site as the most abundant 2-deoxyribose lesion in radiation-damaged DNA using a novel HPLC-based approach.

A novel analytical high-performance liquid chromatography (HPLC)-based method of quantification of the yields of C4'-oxidized abasic sites, 1, in oxidatively damaged DNA has been elaborated. This new approach is based on efficient conversion of 1 into N-substituted 5-methylene-Δ(3)-pyrrolin-2-ones, 2, upon treatment of damaged DNA with primary amines in neutral or slightly acidic solutions with subsequent quantification of 2 by HPLC. The absolute and relative radiation-chemical yields of 1 in irradiated DNA solutions were re-evaluated using this method.

Extracellular ubiquitin inhibits beta-AR-stimulated apoptosis in cardiac myocytes: role of GSK-3beta and mitochondrial pathways.

Aims: Beta-adrenergic receptor (beta-AR) stimulation induces apoptosis in adult rat ventricular myocytes (ARVMs) via the activation of glycogen synthase kinase-3beta (GSK-3beta) and mitochondrial pathways. However, beta-AR stimulation induces apoptosis only in a fraction ( approximately 15-20%) of ARVMs. We hypothesized that ARVMs may secrete/release a survival factor(s) which protects 80-85% of cells from apoptosis.

Binding of the human nucleotide excision repair proteins XPA and XPC/HR23B to the 5R-thymine glycol lesion and structure of the cis-(5R,6S) thymine glycol epimer in the 5'-GTgG-3' sequence: destabilization of two base pairs at the lesion site.

The 5R thymine glycol (5R-Tg) DNA lesion exists as a mixture of cis-(5R,6S) and trans-(5R,6R) epimers; these modulate base excision repair. We examine the 7:3 cis-(5R,6S):trans-(5R,6R) mixture of epimers paired opposite adenine in the 5'-GTgG-3' sequence with regard to nucleotide excision repair. Human XPA recognizes the lesion comparably to the C8-dG acetylaminoflourene (AAF) adduct, whereas XPC/HR23B recognition of Tg is superior.

Selective radiation-induced generation of 2-deoxyribonolactone lesions in DNA mediated by aromatic iodonium derivatives.

2-Deoxyribonolactone lesions were identified as major products of radiation damage to DNA mediated by o,o'-diphenyleneiodonium cations in a hydroxyl radical-scavenging environment. The highest selectivity toward deoxyribonolactone formation (up to 86% of all sugar-phosphate damages) and the overall reaction efficiency (up to 40% of all radiation-generated intermediates converted into products) was displayed by derivatives with positively charged (2-aminoethylthio)acetylamino and (2-aminoethylamino)acetylamino side chains. The reaction can be useful for random single-step incorporation of deoxyribonolactone lesions into single- and double-stranded oligonucleotides and highly polymerized DNA directly in commonly used buffers (PBS, phosphate, Tris-HCl, etc.

Redox-dependent formation of disulfide bonds in human replication protein A.

Human replication protein A (RPA) is a single-stranded DNA (ssDNA)-binding protein with three subunits. The largest subunit, p70, contains a conserved (cysteine)(4)-type zinc-finger motif that has been implicated in the regulation of DNA replication and repair. Previous studies indicated that the ssDNA-binding activity of RPA could be redox-regulated via reversible oxidation of cysteines in the zinc-finger motif.

Structural characterization of human RPA sequential binding to single-stranded DNA using ssDNA as a molecular ruler.

Human replication protein A (RPA), a heterotrimer composed of RPA70, RPA32, and RPA14 subunits, contains four single-stranded DNA (ssDNA) binding domains (DBD): DBD-A, DBD-B, and DBD-C in RPA70 and DBD-D in RPA32. Although crystallographic or NMR structures of these DBDs and a trimerization core have been determined, the structure of the full length of RPA or the RPA-ssDNA complex remains unknown. In this article, we have examined the structural features of RPA interaction with ssDNA by fluorescence spectroscopy.

Diffusion Approach to Long Distance Charge Migration in DNA: Time-Dependent and Steady-State Analytical Solutions for the Product Yields.

In this study we report analytical solutions for both time-dependent and steady-state problems of unbiased charge transfer through a regular DNA sequence via a hopping mechanism. The phenomenon is treated as a diffusion of charge in a one-dimensional array of equally spaced and energetically equivalent temporary trapping sites. The solutions take into account the rates of charge hopping (k), side reactions (k(r)), and charge transfer to a terminal charge acceptor (k(t)).

Specific and efficient binding of xeroderma pigmentosum complementation group A to double-strand/single-strand DNA junctions with 3'- and/or 5'-ssDNA branches.

Human XPA is an important DNA damage recognition protein in nucleotide excision repair (NER). We previously observed that XPA binds to the DNA lesion as a homodimer [Liu, Y., Liu, Y.

Protection of DNA against direct radiation damage by complex formation with positively charged polypeptides.

Radioprotection of DNA from direct-type radiation damage by histones has been studied in model systems using complexes of positively charged polypeptides (PCPs) with DNA. PCPs bind to DNA via ionic interactions mimicking the mode of DNA-histone binding. Direct radiation damage to DNA in films of DNA-PCP complexes was quantified as unaltered base release, which correlates closely with DNA strand breaks.

The release of 5-methylene-2-furanone from irradiated DNA catalyzed by cationic polyamines and divalent metal cations.

Release of 5-methylene-2-furanone (5-MF), a characteristic marker of DNA deoxyribose oxidative damage at the C1' position, was observed in significant quantities from X-irradiated DNA. This observation, which held for DNA irradiated either in aqueous solution or as a film, requires postirradiation treatment at 90 degrees C in the presence of polyamines and divalent metal cations at biological pH. The 5-MF product was quantified by using reverse-phase HPLC.