Repair and replication of oxidized DNA bases using modified oligodeoxyribonucleotides

Modified oligodeoxyribonucleotides (ODNs) are powerful tools to assess the biological significance of oxidized lesions to DNA. For this purpose, we de veloped original synthetic pathways for the site-specific insertion of seve ral oxidized bases into DNA fragments. Thus, the chemical solid-phase synth esis of ODNs using original strategies of protection and mild conditions of deprotection, as well as a specific post-oxidation approach of an unique n ucleoside residue within the sequence have been applied. These two approach es of preparation allowed us to have access to a set of modified ODNs that contain a single modified nucleoside, i.e., N-(2-deoxy-beta-D-erythro-pento furanosyl)formylamine (dF), 5-hydroxy-2'-deoxycytidine (5-OHdCyd), thymidin e glycol (dTg), 5,6-dihydrothymidine (DHdThd), 2,2-diamino-4-[(2-deoxy-beta -D-erythro-pentofuranosyl)-amino]-5(2H)-oxazolone (dZ), N-(2-deoxy-beta-D-e rythro-pentofuranosyl)cyanuric acid (dY), 5',8-cyclo-2'-deoxyguanosine (cyc lodGuo) and 5',8-cyclo-2'-deoxyadenosine (cyclodAdo). The substrates were u sed to investigate recognition and removal of the lesions by bacterial DNA N-glycosylases, including endonuclease III (endo III) and Fapy glycosylase (Fpg). In addition, the DNA polymerase-mediated nucleotide incorporation op posite the damage was determined using modified ODNs as templates. (C) 2000 Societe francaise de biochimie et biologie moleculaire/Editions scientifiq ues et medicales Elsevier SAS.