Transcription activator. Doesn't appear to bind to the consensus 5'-AACAAT-3' DNA binding site, but binds 5'-ATTGTT-3'. All of the sox17 proteins are required for embryonic endoderm development and gastrulation movements, and show some redundancy in function. In addition, the sox17 proteins have distinct but overlapping roles in later gut development. Acts downstream of vegt-signaling in endoderm differentiation to induce a range of endodermal genes both directly and indirectly. Also represses wnt-responsive genes to inhibit wnt/beta-catenin-mediated signaling. Interacts (via C-terminus) with ctnnb1/beta-catenin (via Armadillo repeats); this interaction is required for inhibition of wnt-signaling. In early gastrulae, expressed in the vegetal but not animal hemisphere. The vegetal region is fated to become endoderm and endodermal expression continues throughout gastrulation and neurulation. At tailbud stages, expression is barely detectable. Expressed zygotically from late blastula stage. Expression is barely detectable during tailbud stages and is absent by stage 35 (early tadpole). Involved in multiple regulatory feedback loops with other endodermal factors, including the nodal-related factors/Xnrs. Autoinduces. By activin. Directly by vegt; originally cell-autonomously and then cell contact is required for expression to be maintained. By bmp-signaling. The 9aaTAD motif is a transactivation domain present in a large number of yeast and animal transcription factors.