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N-terminal Mad Homology 1 (MH1) domain in SMAD4 The MH1 is a small DNA-binding domain present in SMAD (small mothers against decapentaplegic) family of proteins, which are signal transducers and transcriptional modulators that mediate multiple signaling pathways. MH1 binds to the DNA major groove in an unusual manner via a beta hairpin structure. It negatively regulates the functions of the MH2 domain, the C-terminal domain of SMAD. This MH1 belongs to SMAD4, a common mediator SMAD (co-SMAD), which belongs to the Dwarfin family of proteins and is involved in many cell functions such as differentiation, apoptosis, gastrulation, embryonic development and cell cycle. SMAD4 binds receptor regulated SMADs (R-SMADs) such as SMAD1 or SMAD2, and forms an oligomeric complex that binds to DNA and serves as a transcription factor. SMAD4 is often mutated in several cancers, such as multiploid colorectal cancer and pancreatic carcinoma, as well as in juvenile polyposis syndrome (JPS).
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