Signal transducer and activator of transcription 1-alpha/beta (STAT1) is a ~87 kDa protein. Signal transducer and transcription activator that mediates cellular responses to interferons (IFNs), cytokine KITLG/SCF and other cytokines and other growth factors. Following type I IFN (IFN-alpha and IFN-beta) binding to cell surface receptors, signaling via protein kinases leads to activation of Jak kinases (TYK2 and JAK1) and to tyrosine phosphorylation of STAT1 and STAT2. The phosphorylated STATs dimerize and associate with ISGF3G/IRF-9 to form a complex termed ISGF3 transcription factor, that enters the nucleus. ISGF3 binds to the IFN stimulated response element (ISRE) to activate the transcription of IFN-stimulated genes (ISG), which drive the cell in an antiviral state. In response to type II IFN (IFN-gamma), STAT1 is tyrosine- and serine-phosphorylated. 1. Rogers, RS. et al. (2003) The Journal of biological chemistry 278, 30091-7. PMID: 127641293. DeVries, TA. et al. (2004) The Journal of biological chemistry 279, 45603-12. PMID: 153221154. Yeh, HM. et al. (2013) Journal of immunology (Baltimore, Md. : 1950) 191, 3328-36. PMID: 239402785. Li, M. et al. (2021) Experimental cell research 407, 112784. PMID: 345087467. Liu, B. et al. (1998) Proceedings of the National Academy of Sciences of the United States of America 95, 10626-31. PMID: 97247549. Zhang, Y. et al. (2015) Nature immunology 16, 1215-27. PMID: 26479788 | 
