Characterization of G3BPs: tissue specific expression, chromosomal localisation and rasGAP(120) binding studies

The G3BP (ras-GTPase-Activating Protein SH3-Domain-Binding Protein) family of proteins has been implicated in both signal transduction and RNA-metabolism. We have previously identified human G3BP-1, G3BP-2, and mouse G3BP-2. Here, we report the cloning of mouse G3BP-1, the discovery of two alternatively spliced isoforms of mouse, and human G3BP-2 (G3BP-2a and G3BP-2b), and the chromosomal localisation of human G3BP-1 and G3BP-2, which map to 5q14.2-5q33.3 and 4q12-4q24 respectively. We mapped the rasGAP(120) interactive region of the G3BP-2 isoforms and show that both G3BP-2a and G3BP-2b use an N-terminal NTF2-like domain for rasGAP(120) binding rather than several available proline-rich (PxxP) motifs found in members of the G3BPs. Furthermore, we have characterized the protein expression of both G3BP-1 and G3BP-2a/b in adult mouse tissues, and show them to be both tissue and isoform specific.