A dominant negative RAS-specific guanine nucleotide exchange factor reverses neoplastic phenotype in K-ras transformed mouse fibroblasts.

Ras proteins are small GTPases playing a pivotal role in cell proliferation and differentiation. Their activation state depends on the competing action of GTPase Activating Proteins (GAP) and Guanine nucleotide Exchange Factors (GEF). A tryptophan residue (Trp1056 in CDC25Mm-GEF), conserved in all ras-specific GEFs identified so far has been previously shown to be essential for GEF activity.