ATF-1 Is Activated in Response to UV Irradiation in B16 Melanoma Cells

We have found that the transferrin receptor gene promoter is strongly activated by exposure of B16 melanoma cells to UV light. This is a delayed event occurring more than 6 h after exposure and requires an AP-1/CRE-like element in the promoter as demonstrated by site-specific mutagenesis. UV irradiation enhances the binding of a nuclear factor to this element and supershift analysis demonstrates that this DNA–protein complex involves ATF-1. No other members of either the AP-1 or CREB/ATF families of transcription factors were found to bind to this DNA element in UV-irradiated B16 cells. Western blots show that the level of ATF-1 does not change following exposure to UV light, indicating that the increased binding of this factor is most likely mediated by posttranslational modifications in response to UV-mediated signaling pathways.