Platelet-derived growth factor generates at least two distinct intracellular signals that modulate gene expression

Platelet-derived growth factor (PDGF) binds to receptors located on the outer cell surface. From there, it stimulates transcription of between 10 and 100 genes within the cell nucleus. The proteins required for these genes to respond to PDGF already exist within the cell because the induction is not blocked by inhibitors of protein synthesis. In this paper, the authors summarize evidence that PDGF generates at least two intracellular second signals and perhaps even more. They show, moreover, that the various competence genes respond selectively to one signal or to the other signals