Dehydration, deamination and enzymatic repair of cytosine glycols from oxidized poly(dG-dC) and poly(dI-dC).

Abstract

Cytosine glycols (5,6-dihydroxy-5,6-dihydrocytosine) are initial products of cytosine oxidation. Because these products are not stable, virtually all biological studies have focused on the stable oxidation products of cytosine, including 5-hydroxycytosine, uracil glycols and 5-hydroxyuracil. Previously, we reported that the lifetime of cytosine glycols was greatly enhanced in double-stranded DNA, thus implicating these products in DNA repair and mutagenesis. In the present work, cytosine and uracil glycols were generated in double-stranded alternating co-polymers by oxidation with KMnO4. The half-life of cytosine glycols in poly(dG-dC) was 6.5 h giving a ratio of dehydration to deamination of 5:1. At high substrate concentrations, the excision of cytosine glycols from poly(dG-dC) by purified endonuclease III was comparable to that of uracil glycols, whereas the excision of these substrates was 5-fold greater than that of 5-hydroxycytosine. Kinetic studies revealed that the V(max) was several fold higher for the excision of cytosine glycols compared to 5-hydroxycytosine. In contrast to cytosine glycols, uracil glycols did not undergo detectable dehydration to 5-hydroxyuracil. Replacing poly(dG-dC) for poly(dI-dC) gave similar results with respect to the lifetime and excision of cytosine glycols. This work demonstrates the formation of cytosine glycols in DNA and their removal by base excision repair.

• Authors: Sébastien Tremblay, J Richard Wagner
• Journal: Nucleic acids research (Nucleic Acids Res) Vol. 36 Issue 1 Pg. 284-93 (Jan 2008) ISSN: 1362-4962 [Electronic] England
• PMID: 18032437 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Polydeoxyribonucleotides
• uracil glycol
• Potassium Permanganate
• cytosine glycol
• poly d(I-C)
• poly(dC-dG)
• Uracil
• Cytosine
• Deoxyribonuclease (Pyrimidine Dimer)
• DNA-Formamidopyrimidine Glycosylase
• DNA Repair Enzymes

Topics

• Cytosine (analogs & derivatives, analysis, chemistry, metabolism)
• DNA Repair
• DNA Repair Enzymes (metabolism)
• DNA-Formamidopyrimidine Glycosylase (metabolism)
• Deamination
• Deoxyribonuclease (Pyrimidine Dimer) (metabolism)
• Kinetics
• Oxidation-Reduction
• Polydeoxyribonucleotides (chemistry, metabolism)
• Potassium Permanganate (chemistry)
• Uracil (analogs & derivatives, analysis)