Nuclear onco-protein targets of signal transduction pathways

Irradiation of mammalian cells with ultraviolet light (200-400 nm) results in the activation of a number of genes, the so-called "UV response" (Herrlich et al., Rev. Physiol. Biochem. Pharmacol., 119:187-223, 1992). Many of the UV responsive genes are also transcriptionally activated by growth factors and mitogens. Two transcription factors have been demonstrated to acutely respond to these stimuli, namely AP-1 and NF-kappa B. Whereas NF-kappa B proteins are primarily controlled via proteolysis of regulatory domains which prevent nuclear translocation, the AP-1 proteins are regulated at several levels including transcription and posttranslational modification. Here, we discuss progress in the identification of the components of pathways acutely regulating these transcription factors.