Signal Transducer And Activator Of Transcription 3 (STAT3)

STAT3, a transcription factor for acute phase response genes, acts as an adaptor molecule in signal transduction from the type I interferon receptor. They found that it binds to a conserved sequence in the cytoplasmic tail of the IFNAR1 chain of the receptor and undergoes interferon-dependent tyrosine phosphorylation. The p85 regulatory subunit of phosphatidylinositol 3-kinase, which activates a series of serine kinases, was found to bind to phosphorylated STAT3 and subsequently to undergo tyrosine phosphorylation. The authors concluded that STAT3 acts as an adaptor to couple another signaling pathway to the interferon receptor.In many human cancers and transformed cell lines, STAT3 is persistently activated, and in cell culture, active STAT3 is either required for transformation, enhances transformation, or blocks apoptosis.