Studies on transcriptional activator properties of tumor suppressor protein p53

Tumor suppressor protein p53 binds to DNA in a sequence-specific manner and activates transcription from promoters near its binding site.It is also known to repress promoters lacking the p53-binding site.In this study, we demonstrate that p53 can act as a transcriptional activator or repressor in vivo using the same reporter with the DNA-binding site CON and these effects depend on the amount of p53 expressed.Both in Saos2 and Cos7 cells, lower concentrations o f p53 lead to activation and higher concentrations lead to repression of the model promoter containing the consensus p53-binding site CON.The N-terminal part o f p53 is necessary for the transcriptional activation.It is not needed, however, for the repression of the same promoter, indicating that different domains o f p53 are involved in activation and repression.