we have found that members of the Ras network of proteins, Ras-GTPase activating protein-SH3-domain-binding proteins 1 and 2 (G3BP1 and 2), bind to p53 in vitro and in vivo. Our data show that expression of G3BPs leads to the redistribution of p53 from the nucleus to the cytoplasm. The G3BP2 isoform additionally associated with murine double minute 2 (MDM2), a negative regulator of p53. G3BP2 expression resulted in significant reduction in MDM2-mediated p53 ubiquitylation and degradation. Interestingly, MDM2 was also stabilized in G3BP2-expressing cells and its ability to ubiquitylate itself was compromised