Binding of the growth suppressor p53 protein to the cell cycle regulator phosphatase cdc25C

Human p53 is a growth suppressor which not only functions in mammalian cell s but also in fission yeast. It was previously shown that the cell cycle re gulating phosphatase cdc25C suppresses the p53 induced growth arrest in fis sion yeast. In the present study we analysed the mechanism of this suppress ion. We found that cdc25C directly interacts with p53. By using different d eletion mutants the binding region was narrowed down on the polypeptide cha in of p53 to amino acids 287-340. To test the functional significance we an alysed the effect of this interaction on the DNA binding activity of p53. A s shown by band shift experiments binding of cdc25C to p53 does not modify the DNA binding activity of p53. Our data suggest that the observed suppres sion of the p53 induced growth arrest by cdc25C might be achieved by direct binding of cdc25C to the C-terminus of p53.