title: Solar UV radiation-induced DNA Bipyrimidine photoproducts: formation and mechanistic insights.
abstract: This review chapter presents a critical survey of the main available information on the UVB and UVA bipyrimidine photoproducts which constitute the predominant recipient classes of photo-induced DNA damage. Evidence is provided that UVB irradiation of isolated DNA in aqueous solutions and in cells gives rise to the predominant generation of cis-syn cyclobutane pyrimidine dimers (CPDs) and, to a lesser extent, of pyrimidine (6-4) pyrimidone photoproducts (6-4PPs), the importance of which is strongly primary sequence dependent. A notable change in the photoproduct distribution is observed when DNA either in the dry or in desiccated microorganisms is exposed to UVC or UVB photons with an overwhelming formation of 5-(α-thymidyl)-5,6-dihydrothymidine, also called spore photoproduct (dSP), at the expense of CPDs and 6-4PPs. UVA irradiation of isolated and cellular DNA gives rise predominantly to bipyrimidine photoproducts with the overwhelming formation of thymine-containing cyclobutane pyrimidine dimers at the exclusion of 6-4PPs. UVA photons have been shown to modulate the distribution of UVB dimeric pyrimidine photoproducts by triggering isomerization of the 6-4PPs into related Dewar valence isomers. Mechanistic aspects of the formation of bipyrimidine photoproducts are discussed in the light of recent photophysical and theoretical studies.
authors.affiliation: Institut Nanosciences et Cryogénie/DSM, CEA-Grenoble, 17 avenue des Martyrs, 38054, Grenoble Cedex 9, France, jean.cadet@cea.fr.
authors.forename: Jean
authors.initials: J
authors.lastname: Cadet
authors.forename: André
authors.initials: A
authors.lastname: Grand
authors.forename: Thierry
authors.initials: T
authors.lastname: Douki
mesh_terms: D001105:Archaea / Q000235:genetics / Q000528:radiation effects; D001419:Bacteria / Q000235:genetics / Q000528:radiation effects; D004247:DNA / Q000737:chemistry / Q000302:isolation & purification / Q000528:radiation effects*; D004249:DNA Damage; D054856:G-Quadruplexes / Q000528:radiation effects; D006801:Humans; D015394:Molecular Structure; D011740:Pyrimidine Dimers / Q000737:chemistry* / Q000302:isolation & purification / Q000528:radiation effects; D012867:Skin / Q000378:metabolism / Q000528:radiation effects; D012996:Solutions; D013237:Stereoisomerism; D013472:Sunlight / Q000009:adverse effects*; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D011740:Pyrimidine Dimers; D012996:Solutions; D004247:DNA