Catenin ?-1 (p120 catenin) has an amino-terminal coiled-coil domain followed by a regulatory domain containing multiple phosphorylation sites and a central Armadillo repeat domain of ten linked 42-amino acid repeats. The carboxy-terminal tail has no known function. Catenin ?-1 fulfills critical roles in the regulation of cell-cell adhesion as it regulates E-cadherin turnover at the cell surface to determine the level of E-cadherin available for cell-cell adhesion. Catenin ?-1 has both positive and negative effects on cadherin-mediated adhesion. Actin dynamics are also regulated by catenin ?-1, which modulates RhoA, Rac, and cdc42 proteins. Analogous to ?-catenin, catenin ?-1 translocates to the nucleus, although its role at this location is unclear. Many studies show that catenin ?-1 is expressed irregularly or is absent in various types of tumor cells, suggesting that catenin ?-1 may function as a tumor suppressor.