Activation of STAT6 is not dependent on phosphotyrosine-mediated docking to the interleukin-4 receptor and can be blocked by dominant-negative mutants of both receptor subunits.
Moriggl R, Erhardt I, Kammer W, Berchtold S, Schnarr B, Lischke A, Groner B, Friedrich K, Eur J Biochem, 1998 Jan 15 - link