Transcription factor and DNA molecules. Molecular model showing the secondary structure (helices) of the transcription factor Brachyury (purple) binding to a molecule of DNA (deoxyribonucleic acid, running horizontally from left to right). Brachyury, also known as T, is a protein that controls the transcription of DNA to RNA (ribonucleic acid) by the enzyme RNA polymerase. RNA is the intermediate product in the formation of a protein from its gene. Brachyury binds to a specific sequence of bases in the DNA called a T-box. Brachyury has been found to be crucial in embryonic development in animals. It is necessary to form the mesoderm, the precursor tissue that eventually develops into the internal organs and bones.