The Rho GTPases have multiple effects on the actin cytoskeleton

The importance for the Rho GTPases Rho, Rac, and Cdc42 for the heterogeneit y of the actin cytoskeleton is well documented. However, there is now an em erging view that they also have important roles in signaling pathways that control gene transcription, cell cycle regulation, apoptosis, and tumor pro gression. Furthermore, not only has the number of pathways which involve Rh o GTPases increased, the number of Rho family members and their regulating proteins has increased considerably. This raises important questions regard ing how specificity is achieved in cell signaling employing Rho GTPases. (C ) 1999 Academic Press.