Signal transducer and activator of transcription 6 fragment, (C54H81N13O15), a peptide with the sequence H2N-Ser-Tyr-Trp-Ser-Asp-Arg-Leu-Ile-Ile-OH, MW= 1152.3. STAT6 is a member of the STAT family of transcription factors[1]. 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[2]. This protein plays a central role in exerting IL4 mediated biological responses[3]. 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), expression of cell surface markers, and class switch of immunoglobulins.

References:
1. Leek JP, Hamlin PJ, BellSM, LenchNJ(1997). "Assignment of the STAT6 gene (STAT6) to human chromosome band 12q13 by in situ hybridization". Cytogenet. Cell Genet. 79 (3–4): 208–9.
2. Kisseleva T, Bhattacharya S, Braunstein J, Schindler CW (2002). "Signaling through the JAK/STAT pathway, recent advances and future challenges". Gene 285 (1–2): 1–24.
3. Shimoda K, van Deursen J, Sangster MY, et al. (1996). "Lack of IL-4-induced Th2 response and IgE class switching in mice with disrupted Stat6 gene". Nature 380 (6575): 630–3.