Distribution and repair of bipyrimidine photoproducts in solar UV-irradiated mammalian cells - Possible role of Dewar photoproducts in solar mutagenesis
D. Perdiz et al., Distribution and repair of bipyrimidine photoproducts in solar UV-irradiated mammalian cells - Possible role of Dewar photoproducts in solar mutagenesis, J BIOL CHEM, 275(35), 2000, pp. 26732-26742
In order to better understand the relative contribution of the different UV
components of sunlight to solar mutagenesis, the distribution of the bipyr
imidine photolesions, cyclobutane pyrimidine dimers (CPD), (6-4) photoprodu
cts ((6-4)PP), and their Dewar valence photoisomers (DewarPP) was examined
in Chinese hamster ovary cells irradiated with WC, UVB, or UVA radiation or
simulated sunlight. The absolute amount of each type of photoproduct was m
easured by using a calibrated and sensitive immune-dot-blot assay. As alrea
dy established for UVC and UVB, we report the production of CPD by UVA radi
ation, at a yield in accordance with the DNA absorption spectrum. At biolog
ically relevant doses, DewarPP were more efficiently produced by simulated
solar light than by WE (ratios of DewarPP to (6-4)PP of 1:3 and 1:8, respec
tively), but were detected neither after UVA nor after UVC radiation, The c
omparative rates of formation for CPD, (6-4)PP and DewarPP are 1:0.25 for U
VC, 1:0.12:0.014 for UVB, and 1:0.18:0.06 for simulated sunlight. The repai
r rates of these photoproducts were also studied in nucleotide excision re
pair-proficient cells irradiated with UVB, UVA radiation, or simulated sunl
ight. Interestingly, DewarPP were eliminated slowly, inefficiently, and at
the same rate as CPD, In contrast, removal of (6-4) photoproducts was rapid
and completed 24 h after exposure, Altogether, our results indicate that,
in addition to CPD and (6-4)PP, DewarPP may play a role in solar cytotoxici
ty and mutagenesis.