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Coiled-coil domain of Signal Transducer and Activator of Transcription (STAT), also called alpha domain This family consists of the coiled-coil (alpha) domain of the STAT proteins (Signal Transducer and Activator of Transcription, or Signal Transduction And Transcription), which are latent cytoplasmic transcriptional factors that play an important role in cytokine and growth factor signaling. STAT proteins regulate several aspects of growth, survival and differentiation in cells. The transcription factors of this family are activated by JAK (Janus kinase) and dysregulation of this pathway is frequently observed in primary tumors and leads to immunosuppression, increased angiogenesis and enhanced survival of tumors. There are seven mammalian STAT family members that have been identified: STAT1, STAT2, STAT3, STAT4, STAT5A, STAT5B and STAT6. STAT proteins consist of six structural regions: N-domain (ND)/protein interaction domain, coiled-coil domain (CCD)/STAT all alpha domain, DNA-binding domain (DBD), linker domain (LK), a Src homology 2 (SH2) domain, and C-terminal transcriptional activation domain (TA) that includes two conserved phosphorylation sites (tyrosine and serine residues). The coiled-coil or alpha domain is an interacting region with other proteins, including IRF-9/p48 for STAT1, c-Jun, StIP1, and GRIM-19 for STAT3, and SMRT with STAT5A and STAT5B. A functional STAT1 mutant (phenylalanine to serine) in this domain region shows significantly decreased protein expression caused by translational/post-translational mechanisms independent of proteasome machinery. The phenylalanine is not conserved in STAT4 and STAT6 that have tight specificity, suggesting a novel potential mechanism of specific activation of STAT proteins. Specifically, STAT3, STAT5, and STAT6, which are continually imported to the nucleus independent of tyrosine phosphorylation, require the conformational structure of their coiled-coil domains. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",