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C-terminal Mad Homology 2 (MH2) domain in SMAD7 The MH2 domain is located at the C-terminus of the SMAD (small mothers against decapentaplegic) family of proteins, which are signal transducers and transcriptional modulators that mediate multiple signaling pathways. The MH2 domain is responsible for type I receptor interaction, phosphorylation-triggered homo- and hetero-oligomerization, and transactivation. It is negatively regulated by the N-terminal MH1 domain, which prevents it from forming a complex with SMAD4. SMAD7, an inhibitory or antagonistic SMAD (I-SMAD), acts as a negative regulator of signaling mediated by the TGF-beta superfamily of ligands, by blocking TGF-beta type 1 and activin association with the receptor as well as access to SMAD2. SMAD7 enhances muscle differentiation, playing pivotal roles in embryonic development and adult homoeostasis. SMAD7 and SMAD6 act as critical mediators for effective TGF-beta I-mediated suppression of Interleukin-1/Toll-like receptor (IL-1R/TLR) signaling through simultaneous binding to Pellino-1, an adaptor protein of interleukin-1 receptor associated kinase 1(IRAK1), via their MH2 domains. Altered expression of SMAD7 is often associated with cancer, tissue fibrosis and inflammatory diseases. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",