SMURF2 is an E3 ubiquitin ligase for AXIN and promotes its ubiquitin-mediated degradation. Ectopic SMURF2 immunoprecipitates both exogenously expressed and endogenous AXIN. AXIN is polyubiquitinated by SMURF2 at lysine 505 both in vitro and in vivo (Kim and Jho, 2012).
