Transcriptional activator. Binds to the DNA sequence 5'-AACAAT-3' (By similarity). 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 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 down-regulated and becomes restricted to the most posterior endoderm and the future liver/gall bladder region. By 3-7 days, endodermal expression is restricted to the gall bladder bud. Also expressed in the embryonic gut, with strong expression in the posterior gut during tailbud stages, but by stage 40, expression rises again in the anterior gut. Expressed at a low level in the adult kidney and spleen. Expressed zygotically from late blastula stage. Expressed at all subsequent stages from 10 (early gastrula) to 35 (early tadpole). Involved in multiple regulatory feedback loops with other endodermal factors, including the nodal-related factors/Xnrs. Autoinduces. Induced by activin. Induced directly by vegt; originally this is in a cell-autonomous fashion but subsequently cell contact is required for expression to be maintained. The 9aaTAD motif is a transactivation domain present in a large number of yeast and animal transcription factors.