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A role for ultraviolet A in solar mutagenesis
E A Drobetsky1, J Turcotte, A Châteauneuf
1Centre de Recherche Guy Bernier, Hôpital Maisonneuve-Rosemont, Montréal, PQ Canada.
Summary
Ultraviolet A (UVA) radiation, not just UVB, significantly contributes to sunlight-induced DNA mutations. UVA exposure causes a high frequency of T-to-G mutations, important for understanding skin cancer development.
Area of Science:
- Molecular biology
- Genetics
- Dermatology
Background:
- Solar ultraviolet (UV) radiation, particularly UVB, is known to cause DNA mutations initiating skin cancer.
- The role of UVA in sunlight mutagenesis and skin carcinogenesis is less understood.
Purpose of the Study:
- To investigate the DNA sequence specificity of mutations induced by UVA and UVB radiation.
- To compare UVA and UVB mutagenesis with simulated sunlight and UVC in Chinese hamster ovary cells.
Main Methods:
- Mutation analysis at the adenine phosphoribosyltransferase locus in Chinese hamster ovary cells.
- Irradiation of cells with UVA (lambda > 350 nm), UVB (lambda > 290 nm), simulated sunlight (lambda >= 310 nm), and UVC (254 nm).
- DNA sequencing to determine the types and frequencies of mutations.
Main Results:
- UVA exposure induced T-->G transversions at a high frequency (up to 50%).
- T-->G transversions were also a significant component (25%) of simulated sunlight-induced mutations.
- This specific mutation type was significantly less frequent in UVB (9%) and UVC (5%) exposed cells.
Conclusions:
- The mutagenic effects of broad-spectrum sunlight are not solely due to UVB radiation.
- UVA radiation plays a critical role in inducing specific types of DNA mutations relevant to photocarcinogenesis.