The exposure of mammalian cells to ultraviolet (u.v.) irradiation leads to activation of transcription factors, such as AP-1 and NFkappaB. It is postulated that the EGF receptor but not protein kinase C (PKC) is the major membrane mediator in UVC-induced signal transduction. We demonstrate here that the antisense oligonucleotides of PKC zeta and the dominant negative mutant of PKC lambda/iota as well as dominant negative PKC zeta markedly blocked UVC-induced AP-1 activity. In contrast, UVC-induced AP-1 activity in cells devoid of the EGF receptor (B82), is not significantly different from that of the stable transfectants with a kinase-deficient EGF receptor (B82M721), or wild-type EGF receptor (B82L). This was found at all UVC irradiation doses and time courses studied, while high levels of EGF-induced AP-1 activity were observed in B82L cells but not in B82 cells. This evidence strongly suggests that atypical PKCs, but not the EGF receptor, is necessary for UVC-induced AP-1 activation in JB6 and B82 cells.