Receptor-regulated SMAD (R-SMAD) that is an intracellular signal transducer and transcriptional modulator activated by TGF-beta (transforming growth factor) and activin type 1 receptor kinases.Binds the TRE element in the promoter region of many genes that are regulated by TGF-beta and,on formation of the SMAD2/SMAD4 complex,activates transcription.May act as a tumor suppressor in colorectal carcinoma.Positively regulates PDPK1 kinase activity by stimulating its dissociation from the 14-3-3 protein YWHAQ which acts as a negative regulator.