Smad pathway is the classic pathway of transforming growth factor（TGF）-β superfamily, including bone morphogenetic protein（BMP） signal transduction. The accumulation of Smad complexes will lead to the excessive activation of gene transcription. Therefore, the degradation of Smad is essential to the regulation of Smad pathway. The ubiquitin proteasome pathway degrades Smad proteins, which play an important role in the regulation of TGF-β family signaling. As the core of the system, Smad ubiquitin regulatory factor are HECT-type ubiquitinprotein ligating enzyme that regulate TGF-β and BMP signaling. In the nucleus, according to related literatures and combined with the latest research advances, we review that the discovery and composition of Smurf-1 and its mechanisms in regulating BMP signaling.
