Ectopic expression of c-jun leads to differentiation of P19 embryonal carcinoma cells.

The product of the c-jun proto-oncogene, a major component of the transcription factor AP1, has been implicated in both positive and negative transcriptional control as well as in transformation. The role of c-jun in early development and differentiation processes, however, is still largely unknown. In this paper we show that ectopic expression of exogenous c-jun sequences leads to differentiation and loss of the transformed phenotype of P19 embryonal carcinoma (EC) cells. The mixed populations of endoderm- and mesoderm-like cells that were obtained after the introduction of c-jun morphologically and biochemically resembled P19 cells differentiated in monolayer by retinoic acid (RA). Furthermore, we provide evidence that direct effects of the c-jun gene product on transcription of the retinoic acid receptor beta (RAR beta) gene may be responsible for the differentiation-promoting potential of c-jun.