Identification of a novel mouse p53 target gene DDA3.

We have identified a novel p53 regulated gene designated DDA3 through differential mRNA display on IW32 erythroleukemia cells containing a temperature sensitive p53 allele, tsp53val-135. DDA3 mRNA induction could be observed in all sublines expressing tsp53val-135 cultured at permissive temperature as well as in NIH3T3 cells undergoing DNA damage. Upregulation of DDA3 could be detected within 2 h after down-shifting the temperature to 32.5 degrees C; upon shifting back to 38.5 degrees C, DDA3 mRNA rapidly degraded with a half-life of less than 2 h. Actinomycin D, but not cycloheximide, inhibited the p53 dependent DDA3 induction, suggesting that the activation is through transcriptional regulation and does not require de novo protein synthesis. DDA3 was expressed in multiple mouse tissues including brain, spleen, lung, kidney and testis. Full-length DDA3 cDNA was cloned and it contained an open reading frame predicted to encode a proline rich protein of 329 amino acids. Overexpression of DDA3 in H1299 lung carcinoma cells suppressed colony formation. These results suggest that DDA3 is a p53-regulated gene that might participate in the p53-mediated growth suppression.