STAT1 Protein, Human (His)

STAT1 is a signal transducer and transcription activator that plays a crucial role in mediating cellular responses to interferons (IFNs), cytokine KITLG/SCF, and various growth factors. Upon binding of type I IFN (IFN-alpha and IFN-beta) to cell surface receptors, STAT1 undergoes tyrosine phosphorylation and forms a dimer with STAT2. This complex, known as ISGF3 transcription factor, translocates to the nucleus and activates the transcription of IFN-stimulated genes (ISG), establishing an antiviral state. In response to type II IFN (IFN-gamma), STAT1 is phosphorylated at both tyrosine and serine residues, forming a homodimer (GAF) that enters the nucleus and binds to the IFN-gamma activated sequence (GAS), driving the expression of target genes and inducing a cellular antiviral state. Additionally, STAT1 becomes activated in response to KITLG/SCF and KIT signaling and may mediate cellular responses to activated FGFR1, FGFR2, FGFR3, and FGFR4. Furthermore, in the small intestine, STAT1 associates with Gasdermin-D and promotes the transcription of CIITA, inducing the formation of type 1 regulatory T (Tr1) cells. STAT1 interacts with various proteins, including PIAS1, IFNAR1, IFNAR2, NMI, CREBBP/CBP, PTK2/FAK1, SRC, ERBB4, PARP9, DTX3L, EP300/p300, and IFNGR1, contributing to its diverse cellular functions.