Oxidation of single-stranded oligonucleotides by carbonate radical anions: Generating intrastrand cross-links between guanine and thymine bases separated by cytosines

Conor Crean, Yuriy Uvaydov, Nicholas Geacintov, Vladimir Shafirovich

Research output: Contribution to journalArticle

Abstract

The carbonate radical anion is a biologically important one-electron oxidant that can directly abstract an electron from guanine, the most easily oxidizable DNA base. Oxidation of the 5′-d(CCTACGCTACC) sequence by photochemically generated CO3•- radicals in low steady-state concentrations relevant to biological processes results in the formation of spiroiminodihydantoin diastereomers and a previously unknown lesion. The latter was excised from the oxidized oligonucleotides by enzymatic digestion with nuclease P1 and alkaline phosphatase and identified by LC-MS/MS as an unusual intrastrand cross-link between guanine and thymine. In order to further characterize the structure of this lesion, 5′-d(GpCpT) was exposed to CO3•- radicals, and the cyclic nature of the 5′-d(GpCpT). cross-link in which the guanine C8-atom is bound to the thymine N3-atom was confirmed by LC-MS/MS, 1D and 2D NMR studies. The effect of bridging C bases on the cross-link formation was studied in the series of 5′-d(GpCnpT) and 5′-d (TpCnpG) sequences with n = 0, 1, 2 and 3. Formation of the G*-T* cross-links is most efficient in the case of 5′-d(GpCpT). Cross-link formation (n=0) was also observed in double-stranded DNA molecules derived from the self-complementary 5′-d(TTACGTACGTAA) sequence following exposure to CO3•- radicals and enzymatic excision of the 5′-d (G*pT*) product.

Original languageEnglish (US)
Pages (from-to)742-755
Number of pages14
JournalNucleic Acids Research
Volume36
Issue number3
DOIs
StatePublished - Feb 2008

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Thymine
Cytosine
Carbonates
Guanine
Oligonucleotides
Anions
Electrons
Biological Phenomena
DNA
Oxidants
Alkaline Phosphatase
Digestion

ASJC Scopus subject areas

  • Genetics

Cite this

Oxidation of single-stranded oligonucleotides by carbonate radical anions : Generating intrastrand cross-links between guanine and thymine bases separated by cytosines. / Crean, Conor; Uvaydov, Yuriy; Geacintov, Nicholas; Shafirovich, Vladimir.

In: Nucleic Acids Research, Vol. 36, No. 3, 02.2008, p. 742-755.

Research output: Contribution to journalArticle

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