Full length mouse Smad7 was used to screen a human chondrocyte cDNA library in a yeast two-hybrid system and PPP1R15A (GADD34) was identified as a binding partner of Smad7. The interaction was confirmed by cotransfection of mouse Smad7 and human PPP1R15A (GADD34) into COS1 cells. The association was positively affected by TGF-beta treatment. Exogenously expressed human TGFB1 receptors and catalytic subunit of PP1, PP1CC, could also be identified in the complex of Smad7 and GADD34. Formation of a complex of TGF-beta receptors, Smad7 and PP1 was dependent on the function of SARA, as shown by expression of dominant negative SARA mutants in COS1 cells. SARA interacts with the catalytic subunit of PP1, likely serving as a membrane anchor for PP1CC (Shi et al. 2004).