THE T-PROTEIN ENCODED BY BRACHYURY IS A TISSUE-SPECIFIC TRANSCRIPTIONFACTOR

The mouse Brachyury (T) gene is required for differentiation of the no tochord and formation of mesoderm during posterior development. Homozy gous embryos lacking T activity do not develop a trunk and tail and di e in utero. The T gene is specifically expressed in notochord and earl y 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 protei n activates expression of a reporter gene in HeLa cells through bindin g to the T site, Thus T is a novel tissue-specific transcription facto r, 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 mesoder m development.