The G12 subfamily of heterotrimeric G proteins, comprised of the Alpha-subunits G-Alpha12 and G-Alpha13, has been implicated as a signaling component in cellular processes ranging from cytoskeletal changes to cell growth and oncogenesis. Activated G-Alpha12 and G-Alpha13 have a molecular weight of 43,000 kDa and they show more than 66% amino acid identity. They stimulate mitogenic signaling pathways leading to the oncogenic transformation of fibroblast cell lines. Recent analyses have indicated that G-Alpha12 and G-Alpha13 regulate cytoplasmic as well as nuclear signaling events through downstream targets such as Ras-, Rac-, Rho-, and CDC42 (Cell Division Cycle-42) dependent pathways, leading to cytoskeletal reorganization and to the activation of MAPK (Mitogen-Activated Protein Kinase), JNK (Jun N-terminal kinase), the Na+-H+(sodium/hydrogen) exchanger, c-Fos, SRE (Serum Response [...]