Fig. 5. Smad transcriptional partners. General models for the recognition and regulation of specific target genes by Smads in concert with DNA-binding adaptors such as FAST and OAZ (model A) and constitutive (e.g. TFE and CBF) or signal-regulated (e.g. AP-1) transcription factors that interact with the MH1 domain upon agonist activation (model B) or with the MH2 domain in the basal state (model C). MH1 and MH2, Smad domains; orange boxes, transactivator domains; SID, Smad interaction domain. Although two Smad DNA sites are depicted in each model, only one may be used in certain response elements.