One-Electron Photooxidation and Site-Selective Strand Cleavage at 5-Methylcytosine in DNA by Sensitization with 2-Methyl-1,4-naphthoquinone-Tethered Oligonucleotides

Tanabe, Kazuhito; Yamada, Hisatsugu; Nishimoto, Sei‐ichi

doi:10.1021/ja071369s

Cited by 25 publications

(23 citation statements)

References 24 publications

(34 reference statements)

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“…It is well known that the methylation of cytosine in DNA increases the rate of hydrolytic deamination (6–8), the rate of photodimerization with UV light (58), the reactivity of neighboring guanine toward electrophiles (59), and can increase base radical cation hole transfer and damage at this site (60). Although attempts have been made to compare the susceptibility of cytosine and 5mC to •OH-induced oxidation, these attempts fall short because they do not measure the majority of products in biological contexts.…”

Section: Discussionmentioning

confidence: 99%

Hydroxyl-radical-induced oxidation of 5-methylcytosine in isolated and cellular DNA

Madugundu

Cadet

Wagner

2014

Nucleic Acids Research

118

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The methylation and oxidative demethylation of cytosine in CpG dinucleotides plays a critical role in the regulation of genes during cell differentiation, embryogenesis and carcinogenesis. Despite its low abundance, 5-methylcytosine (5mC) is a hotspot for mutations in mammalian cells. Here, we measured five oxidation products of 5mC together with the analogous products of cytosine and thymine in DNA exposed to ionizing radiation in oxygenated aqueous solution. The products can be divided into those that arise from hydroxyl radical (•OH) addition at the 5,6-double bond of 5mC (glycol, hydantoin and imidazolidine products) and those that arise from H-atom abstraction from the methyl group of 5mC including 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC). Based on the analysis of these products, we show that the total damage at 5mC is about 2-fold greater than that at C in identical sequences. The formation of hydantoin products of 5mC is favored, compared to analogous reactions of thymine and cytosine, which favor the formation of glycol products. The distribution of oxidation products is sequence dependent in specific ODN duplexes. In the case of 5mC, the formation of 5hmC and 5fC represents about half of the total of •OH-induced oxidation products of 5mC. Several products of thymine, cytosine, 5mC, as well as 8-oxo-7,8-dihydroguanine (8oxoG), were also estimated in irradiated cells.

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Section: Discussionmentioning

confidence: 99%

Hydroxyl-radical-induced oxidation of 5-methylcytosine in isolated and cellular DNA

Madugundu

Cadet

Wagner

2014

Nucleic Acids Research

118

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“…Such negligible strand cleavage at the adjacent guanine bases is consistent with the NQ-sensitized photooxidation of m C in DNA. [12] Thus, the secondary intermediate, the guanine radical cation (GC + ), formed through hole transfer from the primary intermediate m CC…”

Section: Resultsmentioning

confidence: 99%

“…As illustrated in Figure 5, we could detect specific strand cleavage at the was prepared from 3 by standard benzamide protection of the exocyclic amine and subsequent desilylation of the hydroxy groups. The resulting N4-protected 2'-deoxycytidine analogue 5 was converted into 4,4'-dimethoxytrityl derivative 6 and then converted into the corresponding phosphoramidite derivative 7; this was followed by incorporation into DNA by using a DNA synthesizer and conventional b-cya- + intermediate into a C5-methyl carbon-centered radical is involved in the formation of alkali-labile oxidation products, such as 5-(hydroxymethyl)cytosine and/or 5-formylcytosine, [12,15] which lead to selective DNA strand cleavage at the More quantitatively, by using a phenylglyoxylic acid chemical actinometer, [38] the relative quantum yields of AQ-and NQ-photosensitized strand cleavage at the m C site were estimated to be 0.9 10 À5 and 0.6 10…”

Section: Resultsmentioning

confidence: 99%

“…The resulting samples were then analyzed by PAGE, for which the experimental details were described previously. [12] Determination of quantum yields of photosensitized oxidation and strand cleavage reaction: Quantum yield measurements were carried out by using a phenylglyoxylic acid actinometer. [38] The light flux was estimated to be 1.66 10 15 photon s À1 .…”

Section: Methodsmentioning

confidence: 99%

“…[8][9][10][11] Our group has also reported that one-electron oxidation and site-selective Keywords: isotope effects · DNA cleavage · DNA methylation · A C H T U N G T R E N N U N G nucleic acids · photooxidation strand cleavage at an m C base in DNA is caused upon photoirradiation of 2-methyl-1,4-naphthoquinone (NQ)-tethered oligodeoxynucleotides (ODNs). [12] In contrast to oxidative strand cleavage occurring at the target m C site with an oppositely located NQ photosensitizer, the corresponding normal C site, arranged instead of m C in the duplex, underwent no such NQ-photosensitized strand cleavage. In addition, competitive strand cleavage was virtually suppressed at a sequence of adjacent G bases, which have a lower oxidation potential than m C. This striking photooxidative reactivity has been applied to the fluorometric detection of a methylation site in a partial sequence of naturally occurring genomic DNA, by using a combination of m C-selective strand cleavage and an invasive cleavage reaction.…”

Section: Introductionmentioning

confidence: 99%

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Anthraquinone‐Sensitized Photooxidation of 5‐Methylcytosine in DNA Leading to Piperidine‐Induced Efficient Strand Cleavage

Yamada

Kitauchi

Tanabe

et al. 2011

Chemistry A European J

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One-electron photooxidations of 5-methyl-2'-deoxycytidine (d(m)C) and 5-trideuteriomethyl-2'-deoxycytidine ([D(3)]d(m)C) by sensitization with anthraquinone (AQ) derivatives were investigated. Photoirradiation of an aerated aqueous solution containing d(m)C and anthraquinone 2-sulfonate (AQS) afforded 5-formyl-2'-deoxycytidine (d(f)C) and 5-hydroxymethyl-2'-deoxycytidine (d(hm)C) in good yield through an initial one-electron oxidation process. The deuterium isotope effect on the AQS-sensitized photooxidation of d(m)C suggests that the rate-determining step in the photosensitized oxidation of d(m)C involves internal transfer of the C5-hydrogen atom of a d(m)C-tetroxide intermediate to produce d(f)C and d(hm)C. In the case of a 5-methylcytosine ((m)C)-containing duplex DNA with an AQ chromophore that is incorporated into the backbone of the DNA strand so as to be immobilized at a specific position, (m)C underwent efficient direct one-electron oxidation by the photoexcited AQ, which resulted in an exclusive DNA strand cleavage at the target (m)C site upon hot piperidine treatment. In accordance with the suppression of the strand cleavage at 5-trideuterio-methylcytosine observed in a similar AQ photosensitization, it is suggested that deprotonation at the C5-methyl group of an intermediate (m)C radical cation may occur as a key elementary reaction in the photooxidative strand cleavage at the (m)C site. Incorporation of an AQ sensitizer into the interior of a strand of the duplex enhanced the one-electron photooxidation of (m)C, presumably because of an increased intersystem crossing efficiency that may lead to efficient piperidine-induced strand cleavage at an (m)C site in a DNA duplex.

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Oxidatively Generated Nucleobase Modifications in Isolated and CellularDNA

Cadet

Douki

Gasparutto

et al. 2012

Encyclopedia of Radicals in Chemistry, Biology and Materials

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The main oxidation reactions of the main pyrimidine bases (thymine and cytosine) and purine bases (adenine and guanine), and 5‐methylcytosine mediated by hydroxyl radical ( · OH) as well as one‐electron oxidants and singlet oxygen ( 1 O 2 ) leading to about 80 single‐oxidized‐type lesions are reported and the mechanism of their formation critically discussed. In addition, a few complex modifications including tandem base modifications involving either carbon‐centered radical or peroxyl radicals derived from radical oxidation of pyrimidine bases are also described. One may add modifications that arise from initial OH‐mediated hydrogen atom abstraction at C5 and C4 of the 2‐deoxyribose moiety of DNA giving rise to purine 5 ′ ,8‐cyclonucleosides and four diastereomeric aldehyde adducts to opposite cytosine bases in double‐stranded DNA, respectively. With the high level of product identification and thanks to the high sensitivity of high performance liquid chromatography (HPLC)‐electrospray ionization‐tandem mass spectrometry analysis, relevant information is gained on the formation of oxidation products in cells. Thus, 12 single and 5 complexes oxidatively generated base lesions have been detected in cellular DNA on exposure to 1 O 2 , γ rays and high‐intensity ultraviolet C (UVC) laser pulses. The information thus gained is strongly supportive of the oxidation mechanisms that were inferred from mechanistic studies on model systems in aerated aqueous solutions.

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One-Electron Photooxidation and Site-Selective Strand Cleavage at 5-Methylcytosine in DNA by Sensitization with 2-Methyl-1,4-naphthoquinone-Tethered Oligonucleotides

Cited by 25 publications

References 24 publications

Hydroxyl-radical-induced oxidation of 5-methylcytosine in isolated and cellular DNA

Hydroxyl-radical-induced oxidation of 5-methylcytosine in isolated and cellular DNA

Anthraquinone‐Sensitized Photooxidation of 5‐Methylcytosine in DNA Leading to Piperidine‐Induced Efficient Strand Cleavage

Oxidatively Generated Nucleobase Modifications in Isolated and CellularDNA

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