G3BP1 (Ras-GTPase activating protein SH3-domain binding protein 1) directly associates with SH3 domains of GTPase activating proteins (GAPs). It was first discovered by its binding to RasGAP. G3BPs have been shown to be involved in a number of mitogenic signaling pathways. G3BP1 is also known to be over expressed in many human cancers (Kim, 2007) and its expression appears to be inversely correlated with PTEN expression (Kim, 2007). Interestingly, G3BP1, along with G3BP2, has been shown to bind to the C-terminus of p53, playing a crucial role in its activity (Kim, 2007). Furthermore, the G3BPs have two traditional RNA binding motifs.