TI - p120 Catenin-associated Fer and Fyn tyrosine kinases regulate beta-catenin Tyr-142 phosphorylation and beta-catenin-alpha-catenin Interaction . AB - beta-Catenin has a key role in the formation of adherens junction through its interactions with E-cadherin and alpha-catenin . We show here that interaction of beta-catenin with alpha-catenin is regulated by the phosphorylation of beta-catenin Tyr-142 . This residue can be phosphorylated in vitro by Fer or Fyn tyrosine kinases . Transfection of these kinases to epithelial cells disrupted the association between both catenins . We have also examined whether these kinases are involved in the regulation of this interaction by K-ras . Stable transfectants of the K-ras oncogene in intestinal epithelial IEC18 cells were generated which show little alpha-catenin-beta-catenin association with respect to control clones ; this effect is accompanied by increased Tyr-142 phosphorylation and activation of Fer and Fyn kinases . As reported for Fer , Fyn kinase is constitutively bound to p120 catenin ; expression of K-ras induces the phosphorylation of p120 catenin on tyrosine residues increasing its affinity for E-cadherin and , consequently , promotes the association of Fyn with the adherens junction complex . Yes tyrosine kinase also binds to p120 catenin but only upon activation , and stimulates Fer and Fyn tyrosine kinases . These results indicate that p120 catenin acts as a docking protein facilitating the activation of Fer/Fyn tyrosine kinases by Yes and demonstrate the role of these p120 catenin-associated kinases in the regulation of beta-catenin-alpha-catenin interaction .