Signaling from strange places

The tumor suppressor p53 can act as a transcription factor, but only a few p53-activated genes have been found, and the biochemical basis of p53-mediated apoptosis has been especially difficult to probe. Now, Bourdon et al. describe the discovery and characterization of a novel p53-inducible proapoptotic gene (page 235).

By comparing gene expression in normal and p53-knockout mice exposed to ionizing radiation, the authors identified Scotin, a novel gene that is directly trans-activated when p53 binds to a specific site in its promoter. Mouse Scotin and its human homologue appear to induce apoptosis in a caspase-dependent manner.

Scotin has the structure of a type I transmembrane receptor, but is located in the endoplasmic reticulum and the nuclear membrane, not in the Golgi apparatus, mitochondria, or plasma membrane. The authors...