Signal transducer and activator of transcription 3
The stat proteins (Stat1-6) function both as cytoplasmic signal transducers and as activators of transcription in response to cytokines and growth factor receptors. Stat3 is expressed as two variants, Stat3alpha (86 kDa) and Stat3b (79 kDa) that can differ in expression and activity depending on cell type, activation pathway, and cell maturation stage. Both are activated by phosphorylation at Tyr-705, which induces dimerization, nuclear translocation and DNA binding. Stat3alpha (86 kDa) transcriptional activation may be regulated by phosphorylation at Ser-727 through the MAPK pathway, while Stat3beta lacks this serine site.
