STATs (signal transducers and activators of transcription) are a family of cytoplasmic latent transcription factors that are activated to regulate gene expression in response to a large number of extracellular signaling polypeptides including cytokines, interferons, and growth factors. After phosphorylation by JAK tyrosine kinases, STATs enter the nucleus to regulate transcription of many different genes. Among the seven STATs (Stat1, Stat2, Stat3, Stat4, Stat5a, Stat5b, and Stat6), Stat1, Stat3, Stat5a, and Stat5b have a wide activation profile (4,5). Human Stat2 cDNA codes for a 851 amino acid protein with a predicted molecular weight of 113 kDa (3). STAT2 associates with beta subunit of the type I IFN receptor in an interferon-dependent manner (1-3).
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