Cytoplasmic transcription factors: mediators of cytokine signaling.

The distinct pattern of transcriptional responses of cells to different extracellular signals requires a signal transduction pathway that provides rapid, accurate, and faithful transmission of information from the cell surface to the nucleus. One mechanism exploited by many cytokines, exemplified by interferons (IFN) but also used by many interleukins and growth factors, uses a family of cytoplasmic transcription factors that are activated by tyrosine phosphorylation. Once phosphorylated by receptor-associated tyrosine kinases, these proteins assemble into multimeric transcription factors, translocate to the nucleus, and bind specific DNA sequence elements in the promoters of target genes.