THE BRACHYURY GENE ENCODES A NOVEL DNA-BINDING PROTEIN

Brachyury (T) mutant embryos are deficient in mesoderm formation and d o not complete axial development. The notochord is most strongly affec ted. The T gene is expressed transiently in primitive streak-derived n ascent and migrating mesoderm cells and continuously in the notochord. Ectopic expression of T protein in the animal cap of Xenopus embryos results in ectopic mesoderm formation. The T protein is located in the nucleus. These and other data suggested that the T gene might be invo lved in the control of transcriptional regulation. In an attempt to de monstrate specific DNA binding of the T protein we have identified a c onsensus sequence among DNA fragments selected from a mixture of rando m oligomers. Under our experimental conditions T protein binds as a mo nomer to DNA. This property resides in the N-terminal domain of 229 am ino acid residues which is strongly conserved between the mouse protei n, and its Xenopus and zebrafish homologues. The latter proteins also recognize the consensus DNA binding site. We suggest that the T protei n is involved in the control of genes required for mesoderm formation, and for the differentiation and function of chorda mesoderm.