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 (including endodermin and dhh/chh) and indirectly. Also represses wnt-responsive genes to inhibit wnt/beta-catenin-mediated signaling (By similarity). Interacts (via C-terminus) with ctnnb1/beta-catenin (via Armadillo repeats); this interaction is required for inhibition of wnt-signaling. Expressed throughout all the deep and superficial endoderm during gastrulation. Expression then declines rapidly after gastrulation, however a small patch of endoderm cells behind the cement gland maintains expression even into tailbud stages. The 9aaTAD motif is a transactivation domain present in a large number of yeast and animal transcription factors.