STAT3

Signal transducer and activator of transcription 3, also known as STAT3, is a transcription factor which in humans is encoded by the STAT3 gene.

Function

STAT3 is a member of the STAT protein family. In response to cytokines and growth factors, STAT3 is phosphorylated by receptor-associated Janus kinases (JAK), form homo- or heterodimers, and translocate to the cell nucleus where they act as transcription activators. Specifically, STAT3 becomes activated after phosphorylation of tyrosine 705 in response to such ligands as interferons, epidermal growth factor (EGF), Interleukin (IL-)5 and IL-6. Additionally, activation of STAT3 may occur via phosphorylation of serine 727 by Mitogen-activated protein kinases (MAPK) and through c-src non-receptor tyrosine kinase. STAT3 mediates the expression of a variety of genes in response to cell stimuli, and thus plays a key role in many cellular processes such as cell growth and apoptosis.

STAT3-deficient mouse embryos cannot develop beyond embryonic day 7, when gastrulation begins. It appears that at these early stages of development, STAT3 activation is required for self-renewal of embryonic stem cells (ESCs). Indeed, LIF, which is supplied to murine ESC cultures to maintain their undifferentiated state, can be omitted if STAT3 is activated through some other means.