Smad ubiquitination regulatory factor 2 (Smurf2), a ubiquitin ligase for Smad, plays a key regulatory role in the TGF-β signaling pathway during renal fibrosis, which is mainly dependent on the degradation of ubiquitinated Smad7 and Smad2 [74]. The gene discussed is SMURF2; the disease is renal fibrosis.