INVOLVEMENT OF GROWTH-FACTOR RECEPTORS IN THE MAMMALIAN UVC RESPONSE

Irradiation of HeLa cells with short-wavelength ultraviolet light (UVC ) induces the modification and activation of the preexisting transcrip tion factors c-fos-c-Jun (AP-1) and TCF/Elk-1, as well as the protein synthesis independent transcriptional activation of the c-fos and c-ju n genes. This response to UVC is mediated via obligatory cytoplasmic s ignal transduction, involving Pas and Raf, Src, and MAP kinases. The U VC response is inhibited by prior down-modulation of growth factor rec eptor signaling upon growth factor prestimulation, by suramin (an inhi bitor of receptor activation) or by expression of a dominant negative epidermal growth factor (EGF) receptor mutant. These data suggest the involvement of several growth factor receptors in the UVC response. In deed, UVC induces the suramin-inhibitable immediate tyrosine phosphory lation of the EGF receptor.