The phosphoprotein p53 is down-regulated post-transcriptionally during embryogenesis in vertebrates.

The phosphoprotein p53 has been investigated mainly because of its relationship with tumorigenic transformation. In this communication, we report that, during the embryonal development of mouse and chicken, there is a decline in the steady-state levels of the p53 protein and an equal decline in p53 mRNA. During the development of the chicken, the relative rates of p53 transcription appear to be constant. p53 mRNA is relatively stable (half-life greater than 12 h) in both chicken and mouse embryos. We conclude that (i) the down-modulation of p53 mRNA (and of protein) during embryonal development has been well conserved during the evolution of the vertebrate, implying that the p53 protein may have a function in embryonal development; and (ii) the mechanism of control is apparently mainly on a post-transcriptional level.