Fos and jun: two into one will go.

c-jun was the first oncogene to be identified as a transcription factor thus realizing the long-standing prediction that gene regulation plays a fundamental role in growth control. Not so predictable was that this protein is assisted in its function by a second proto-oncogene, c-fos; that the transcription factor they help comprise transducers hormonal signals; and that each are the archetypal members of gene families. Here, I describe the remarkable progress that has been made from the initial characterization of these oncogenes to our current understanding of their normal cellular function.