SMURF1, recruited to tight junctions through association with phosphorylated PARD6A, ubiquitinates RHOA, leading to RHOA degradation and disassembly of tight junctions (Ozdamar et al. 2005). Disassembly of tight junctions is an important step in epithelial to mesenchymal transition. SMURF1, but not SMURF2, decreases RHOA level, and this effect is proteasome dependent (Wang et al. 2003).