Unrepaired cyclobutane pyrimidine dimers do not prevent proliferation of UV-B-irradiated cultured human fibroblasts.
Mutagenic and carcinogenic UV-B radiation is known to damage DNA mostly through the formation of bipyrimidine photoproducts, including cyclobutane dimers (CPD) and (6-4) photoproducts ((6-4) PP). Using high-performance liquid chromatography coupled to tandem mass spectrometry, we investigated the formation and repair of thymine-thymine (TT) and thymine-cytosine (TC) CPD and (6-4) PP in the DNA of cultured human dermal fibroblasts. A major observation was that the rate of repair of the photoproducts did not depend on the identity of the modified pyrimidines. In addition, removal of CPD was found to significantly decrease with increasing applied UV-B dose, whereas (6-4) PP were efficiently repaired within less than 24 h, irrespective of the dose. As a result, a relatively large amount of CPD remained in the genome 48 h after the irradiation. Because the overall applied doses (<500 J m(-2)) were chosen to induce moderate cytotoxicity, fibroblasts could recover their proliferation capacities after transitory cell cycle arrest, as shown by 5-bromo-2'-deoxyuridine (BrdUrd) incorporation and flow cytometry analysis. It could thus be concluded that UV-B-irradiated cultured primary human fibroblasts normally proliferate 48 h after irradiation despite the presence of high levels of CPD in their genome. These observations emphasize the role of CPD in the mutagenic effects of UV-B.
Courdavault
Sophie
S
Laboratoire Lésions des Acides Nucléiques, Service de Chimie Inorganique et Biologique, CEA/DSM/Département de Recherche Fondamentale sur la Matière Condensée, CEA-Grenoble, France.
Baudouin
Caroline
C
Sauvaigo
Sylvie
S
Mouret
Stéphane
S
Candéias
Serge
S
Charveron
Marie
M
Favier
Alain
A
Cadet
Jean
J
Douki
Thierry
T
D001973:Bromodeoxyuridine / Q000032:analysis / Q000378:metabolism / Q000528:radiation effects; D002455:Cell Division / Q000528:radiation effects; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000378:metabolism / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts; D006801:Humans; D013058:Mass Spectrometry; D016296:Mutagenesis / Q000528:radiation effects; D011740:Pyrimidine Dimers / Q000032:analysis / Q000378:metabolism* / Q000528:radiation effects; D013997:Time Factors; D014466:Ultraviolet Rays
D011740:Pyrimidine Dimers; D004247:DNA; D001973:Bromodeoxyuridine