Inhibiting the Inhibitor: The Role of RNF12 in TGF-β Superfamily Signaling

In this issue of Molecular Cell , Zhang et al. (2012) identify the E3 ubiquitin ligase RNF12 as a new component of the TGF-β superfamily signaling pathways, which functions by targeting the negative regulator Smad7 for proteasomal degradation and thus potentiates pathway activity.