S71 phosphorylation inhibits activation of Rac1 and Cdc42.169,170 In a recent study, S71 phosphorylation mediates the interaction between Rac1 and 14-3-3, an important scaffold protein involved in multiple signaling pathways.171 Multiple lysines in RhoA and Rac1 are involved in ubiquitination-dependent proteasome degradation, which regulates the protein expression level and impact on cytoskeleton dynamics and cell migration.172–175 HACE1 E3 ubiquitin-ligase, a tumor-suppressor, catalyzes ubiquitination and recruits Ubiquitin-proteasome system preferentially to the activated Rac1. This evidence concerns the gene RAC1 and neoplasm.