title: UVA-induced cyclobutane pyrimidine dimers form predominantly at thymine-thymine dipyrimidines and correlate with the mutation spectrum in rodent cells.
abstract: Ligation-mediated PCR was employed to quantify cyclobutane pyrimidine dimer (CPD) formation at nucleotide resolution along exon 2 of the adenine phosphoribosyltransferase (aprt) locus in Chinese hamster ovary (CHO) cells following irradiation with either UVA (340-400 nm), UVB (295-320 nm), UVC (254 nm) or simulated sunlight (SSL; lambda > 295 nm). The resulting DNA damage spectrum for each wavelength region was then aligned with the corresponding mutational spectrum generated previously in the same genetic target. The DNA sequence specificities of CPD formation induced by UVC, UVB or SSL were very similar, i.e., in each case the overall relative proportion of this photoproduct forming at TT, TC, CT and CC sites was approximately 28, approximately 26, approximately 16 and approximately 30%, respectively. Furthermore, a clear correspondence was noted between the precise locations of CPD damage hotspots, and of 'UV signature' mutational hotspots consisting primarily of C-->T and CC-->TT transitions within pyrimidine runs. However, following UVA exposure, in strong contrast to the above situation for UVC, UVB or SSL, CPDs were generated much more frequently at TT sites than at TC, CT or CC sites (57% versus 18, 11 and 14%, respectively). This CPD deposition pattern correlates well with the strikingly high proportion of mutations recovered opposite TT dipyrimidines in UVA- irradiated CHO cells. Our results directly implicate the CPD as a major promutagenic DNA photoproduct induced specifically by UVA in rodent cells.
authors.affiliation: Division of Pathology, Department of Medical Biology, Faculty of Medicine, Laval University and Unité de Recherche en Génétique Humaine et Moléculaire, Hôpital Saint-François d'Assise, Centre Hospitalier Universitaire de Québec, Québec, QC G1L 3L5, Canada.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Rochette
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Therrien
authors.forename: Régen
authors.initials: R
authors.lastname: Drouin
authors.forename: Daniel
authors.initials: D
authors.lastname: Perdiz
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bastien
authors.forename: Elliot A
authors.initials: EA
authors.lastname: Drobetsky
authors.forename: Evelyne
authors.initials: E
authors.lastname: Sage
mesh_terms: D000228:Adenine Phosphoribosyltransferase / Q000235:genetics; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004249:DNA Damage; D004252:DNA Mutational Analysis; D005091:Exons; D016296:Mutagenesis; D009154:Mutation; D016133:Polymerase Chain Reaction; D011740:Pyrimidine Dimers / Q000032:analysis / Q000378:metabolism / Q000528:radiation effects*; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D011740:Pyrimidine Dimers; D000228:Adenine Phosphoribosyltransferase