The T transcription factor functions as a dimer and exhibits a common human polymorphism Gly-177-Asp in the conserved DNA-binding domain.

T is a transcription factor which activates transcription by binding to repeated arrangements of the dodecamer 5'-AGGTGTGAAATT-3'. Using in vitro synthesised T protein, we have demonstrated that T binds to its target DNA as a homodimer and that truncated protein containing only the N-terminal 233 amino-acid residues, which comprise the DNA-binding domain, can form a dimer. We also report a common human polymorphism, Gly-177-Asp, within the DNA-binding domain at a position which is a conserved glycine residue in T homologues from other vertebrates. The proposition that T forms heterodimers with other members of the T-box transcription factor family and the implications for disorders of axial development are discussed.