WAVELENGTH-SPECIFIC INDUCTION OF IMMEDIATE-EARLY GENES BY ULTRAVIOLET-RADIATION

Exposure of skin in vivo to ultraviolet B (UVB) or ultraviolet A (UVA) radiation produces a variety of distinct clinical manifestations. In the present study, we characterized the immediate early genes that are activated in an epidermoid carcinoma cell line (A431) when exposed to UVB (FS20 sunlamp) or UVA radiation (window glass-filtered black ligh t). We observed that: (a) c-jun mRNA expression is upregulated predomi nantly by UVB; (b) fra-1 and c-myc are downregulated by UVB, whereas b oth are upregulated by UVA; (c) fra-2 and AP-2 are downregulated modes tly by UVB, (d) c-fos is unaffected, and (e) optimal regulation of eac h gene is achieved at environmentally relevant fluences (25-100 J/m(2) for UVB and 2500-10 000 J/m(2) for UVA). Thus, distinct sets of genes are activated (or repressed) by UVB and UVA irradiation. Treatment wi th organic hydrogen peroxides mimicked UVB radiation in upregulating c -jun expression, suggesting the participation of reactive oxygen inter mediates in the UVB-signaling pathway. We propose that wavelength-spec ific regulation of nuclear mediator genes accounts for the development of at least some of the wavelength-specific cutaneous manifestations of ultraviolet radiation.