Regulation of Proto-oncogene fos: A Paradigm for Early Response Genes

Proto-oncogenes have been postulated to play a pivotal role in cell growth, differentiation, and development. They can be functionally divided into three broad classes, which also correspond to different cellular localizations: (1) growth factors and receptors, (2) mediators of intracellular signal transduction pathways, and (3) trans-regulators of transcription (Bishop 1987). A scheme for the physiological interactions and cooperation between the products of the three different classes leading to cell proliferation or differentiation is proposed in Figure 1. Growth factors presumably bind to their cognate receptors and activate a cascade of intracellular events culminating in modulation of gene expression. It is noteworthy that several oncogene products are critically placed in the pathway of transduction of external signals to the nucleus (Fig. 1). Since the final destination of the impact of external stimulus is ensconced in the nucleus, our laboratory in the past several years has elected to study nuclear oncogenes. In...