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.