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. Author manuscript; available in PMC: 2008 Dec 25.
Published in final edited form as: Cell Res. 2008 Feb;18(2):254–267. doi: 10.1038/cr.2008.18

Figure 2.

Figure 2

Activation of the STAT signaling pathway. STAT activation is induced by the binding of ligands, such as growth factors and cytokines to their cognate receptors (R) on the cell surface, which initiates the phosphorylation of the critical tyrosyl residue of STATs by growth factor receptor Tyr kinases (RTKs) or by non-receptor Tyr kinases (NRTKs), such as Jaks, Src or Abelson (Abl) kinase. NRTKs can also directly phosphorylate STATs in the absence of ligand-binding to receptors. Tyr-phosphorylated and activated STAT monomers engage in reciprocal pTyr-SH2 domain interactions for dimerization, and the resulting dimers translocate to the nucleus to regulate the transcription of specific genes by binding to specific STAT-responsive promoter sequences.