MEN1 (menin), a transcription factor tumor suppressor mutated in a familial cancer syndrome multiple endocrine neoplasia type 1, binds SMAD2/3:SMAD4 heterotrimer through interaction with SMAD3. MEN1 likely acts as a trancriptional cofactor for SMAD2/3:SMAD4 and may be involved in transcriptional regulation of some SMAD2/3:SMAD4 target genes (Kaji et al. 2001, Sowa et al. 2004, Canaff et al. 2012).