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SMAD4A gene on chromosome 18q21.1 that encodes a SMAD family protein, named for their similarity to the Drosophila gene Mothers Against Decapentaplegic (MAD), which are signal transducers and transcription modulators of multiple signalling pathways. SMAD4 forms homomeric complexes and heteromeric complexes with other activated SMADs; these accumulate in the nucleus and regulate target gene transcription. SMAD4 binds to DNA and recognizes an 8-bp palindromic sequence, the SMAD-binding element (SBE).
SMAD4 mutations or deletions are linked to hereditary haemorrhagic telangiectasia syndrome, juvenile polyposis syndrome and pancreatic cancer.