title: Chemical synthesis of oligodeoxyribonucleotides containing the Dewar valence isomer of the (6-4) photoproduct and their use in (6-4) photolyase studies.
abstract: The pyrimidine(6-4)pyrimidone photoproduct, a major UV lesion formed between adjacent pyrimidine bases, is transformed to its Dewar valence isomer upon exposure to UVA/UVB light. We have synthesized a phosphoramidite building block of the Dewar photoproduct formed at the thymidylyl(3'-5')thymidine site and incorporated it into oligodeoxyribonucleotides. The diastereoisomers of the partially protected dinucleoside monophosphate bearing the (6-4) photoproduct, which were caused by the chirality of the phosphorus atom, were separated by reversed-phase chromatography, and the (6-4) photoproduct was converted to the Dewar photoproduct by irradiation of each isomer with Pyrex-filtered light from a high-pressure mercury lamp. The Dewar photoproduct was stable under both acidic and alkaline conditions at room temperature. After characterization of the isomerized base moiety by NMR spectroscopy, a phosphoramidite building block was synthesized in three steps. Although the ordinary method could be used for the oligonucleotide synthesis, benzimidazolium triflate as an alternative activator yielded better results. The oligonucleotides were used for the analysis of the reaction and the binding of Xenopus (6-4) photolyase. Although the affinity of this enzyme for the Dewar photoproduct-containing duplex was reportedly similar to that for the (6-4) photoproduct-containing substrate, the results suggested a difference in the binding mode.
authors.affiliation: Division of Chemistry, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Junpei
authors.initials: J
authors.lastname: Yamamoto
authors.forename: Kenichi
authors.initials: K
authors.lastname: Hitomi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Todo
authors.forename: Shigenori
authors.initials: S
authors.lastname: Iwai
mesh_terms: D000818:Animals; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000737:chemistry / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis* / Q000737:chemistry / Q000528:radiation effects; D009943:Organophosphorus Compounds / Q000737:chemistry; D013237:Stereoisomerism; D014466:Ultraviolet Rays; D014982:Xenopus laevis
chemical_list: D009838:Oligodeoxyribonucleotides; D009943:Organophosphorus Compounds; C434331:phosphoramidite; C098727:pyrimidine(6-4)pyrimidone photolyase; D004255:Deoxyribodipyrimidine Photo-Lyase