Smad2 is a 58 kDa member of a family of proteins involved in cell proliferation, differentiation and development. The Smad family is divided into three subclasses: receptor-regulated Smad's, activin/TGFa receptor-regulated (Smad2 and 3) or BMP receptor regulated (Smad1, 5, and 8); the common partner, (Smad4) that functions via its interaction to the various Smad's; and the inhibitory Smad's, (Smad6 and Smad7). Smad2 consists of two highly conserved domains, the N terminal Mad homology (MH1) and the C-terminal Mad homology 2 (MH2) domains. The MH1 domain binds DNA and regulates nuclear import and transcription while the MH2 domain conserved among all the Smad's regulates Smad2 oligomerization and binding to cytoplasmic adaptors and transcription factors. Activated Smad2 associates with Smad4 and translocates as a complex into the nucleus, allowing its binding to DNA and transcription factors. This translocation of Smad2 (as well as Smad3) into the nucleus is a central event in TGF beta signaling.