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Synthesis and enzymatic processing of oligodeoxynucleotides containing tandem base damage
A G Bourdat1, D Gasparutto, J Cadet
1Laboratoire des Lésions des Acides Nucléiques, Service de Chimie Inorganique et Biologique, Département de Recherche Fondamentale sur la Matière Condensée, CEA-Grenoble, F-38054 Grenoble Cedex 9, France.
Nucleic Acids Research
|February 3, 1999
Summary
Ionizing radiation causes DNA damage, including tandem base lesions like 8-oxodGuo. Researchers synthesized and analyzed these DNA lesions to understand their biological significance and repair mechanisms.
Area of Science:
- Biochemistry
- Molecular Biology
- Radiation Chemistry
Background:
- Ionizing radiation induces diverse DNA lesions, including base modifications, strand breaks, and crosslinks.
- Tandem base damage, specifically N-(2-deoxy-beta-d-erythro-pentofuranosyl)-formylamine/8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), is a significant lesion induced by hydroxyl radicals in irradiated DNA oligomers.
- Understanding the biological implications of such complex DNA lesions is crucial for comprehending cellular responses to radiation exposure.
Purpose of the Study:
- To synthesize and characterize vicinal tandem DNA lesions, specifically 8-oxodGuo and formylamine.
- To investigate the alkaline lability and biochemical properties of these multiply damaged DNA sites.
- To assess the processing of these lesions by various nucleases and DNA repair enzymes.
Main Methods:
- Solid-phase phosphoramidite method for synthesizing modified oligonucleotides.
- Development of a novel synthesis for 8-oxodGuo.
- Purity and integrity assessment using HPLC, polyacrylamide gel electrophoresis, electrospray, and MALDI-TOF mass spectrometry.
- Piperidine test for alkaline lability.
- Enzymatic assays with nucleases (P1, snake venom phosphodiesterase, calf spleen phosphodiesterase) and repair enzymes (E. coli endonuclease III, Fapy-glycosylase).
Main Results:
- Successful synthesis of oligonucleotides containing vicinal 8-oxodGuo and formylamine lesions.
- Demonstration of high alkaline lability of the formylamine moiety within the DNA.
- Characterization of the processing of these tandem lesions by specific enzymatic activities, providing insights into their repair.
- The study reports on the enzymatic processing of these vicinal lesions by various enzymes.
Conclusions:
- The study successfully synthesized and characterized complex tandem DNA lesions, contributing to the understanding of DNA damage induced by ionizing radiation.
- The findings highlight the alkaline lability of formylamine in DNA and provide insights into the enzymatic repair pathways for such multiply damaged sites.
- This research lays the groundwork for further investigations into the biological significance and mutagenic potential of tandem base damage in DNA.