Figure 2

The TGFβ signal-transduction pathway. Ligand binding induces activation of TGFβ receptor complexes, which then directly phosphorylate (P) specific R-Smads. These R-Smads associate with the common (co) Smad Smad4 and then translocate to the nucleus, where they interact with a variety of DNA-binding partners to regulate gene expression. See text for further details.