After ubiquitination by RNF111 (Arkadia), ubiquitinated SMAD7 is degraded in a proteasome dependent way. Therefore, RNF111 has a positive effect on transcription initiated by TGF-beta signaling. However, TGF-beta signaling ultimately results in a decrease of RNF111 mRNA level, enabling negative-feedback regulation of TGF-beta signal by SMAD7. RNF111 may fine tune the duration of cellular response to TGF-beta signal. Initially, RNF111 may enable signal propagation by inhibiting negative regulators of TGF-beta signaling, SKI/SKIL and SMAD7. Subsequent negative regulation of RNF111 expression by TGF-beta may allow the signaling cascade to be turned off (Koinuma et al. 2003).