The protein encoded by this gene is a member of the STAT family of transcription factors. In response to cytokines and growth factors, STAT family members are phosphorylated by the receptor associated kinases, and then form homo- or heterodimers that translocate to the cell nucleus where they act as transcription activators. This protein plays a central role in exerting IL4 mediated biological responses. It is found to induce the expression of BCL2L1/BCL-X(L), which is responsible for the anti-apoptotic activity of IL4. Knockout studies in mice suggested the roles of this gene in differentiation of T helper 2 (Th2) cells, expression of cell surface markers, and class switch of immunoglobulins. Alternative splicing results in multiple transcript variants.[provided by RefSeq, May 2010],function:Carries out a dual function: signal transduction and activation of transcription. Involved in interleukin-4 signalling.,PTM:Tyrosine phosphorylated following stimulation by IL-4 and IL-3.,similarity:Belongs to the transcription factor STAT family.,similarity:Contains 1 SH2 domain.,subcellular location:Translocated into the nucleus in response to phosphorylation.,subunit:Forms a homodimer or a heterodimer with a related family member (By similarity). Interacts with NCOA1 via its C-terminal LXXLL motif.,