The T protein encoded by Brachyury is a tissue-specific transcription factor.

The mouse Brachyury (T) gene is required for differentiation of the notochord and formation of mesoderm during posterior development. Homozygous embryos lacking T activity do not develop a trunk and tail and die in utero. The T gene is specifically expressed in notochord and early mesoderm cells in the embryo. recent data have demonstrated that the T protein is localized in the cell nucleus and specifically binds to a palindrome of 20 bp (the T site) in vitro. We show that the T protein activates expression of a reporter gene in HeLa cells through binding to the T site. Thus T is a novel tissue-specific transcription factor. It consists of a large N-terminal DNA binding domain (amino acids 1-229) and two pairs of transactivation and repression domains in the C-terminal protein half. T can also transactivate transcription through variously oriented and spaced T sites, a fact that may be relevant in the search for genes controlled by T protein and important in mesoderm development.