Two-dimensional gel mapping of small GTPases reveals transformation-specific changes during oncogenesis

Epithelial cells transformed by oncogenes in vitro change their gene expression program, thereby losing features of cell polarity and cell adhesion. Using ras-transformed mammary epithelial cells, we have investigated the expression of other small GTP-binding proteins by high-resolution two-dimensional gel electrophoresis and direct GTP ligand binding after renaturing transfer onto nitrocellulose. Ras-transformed cells lost the expression of one epithelial-specific GTP-binding protein (21-22 kDa, pI 4.5-4.8) and instead expressed a fibroblast GTP-binding protein (21-22 kDa, pI 4.8-5.0).