A COMMON ANCESTOR OF THE MAMMALIAN TRANSCRIPTION FACTORS TCF-1 AND TCF-1-ALPHA/LEF-1 EXPRESSED IN CHICKEN T-CELLS

Several mammalian T cell-specific transcription factors have been cloned recently. Two of these, TCF-1 and TCF-1-alpha/LEF-1, display a moderate level of overall sequence similarity, and contain virtually identical versions of a novel type of DNA-binding domain, the HMG box. To study evolutionary aspects of the TCF transcription factors in relation to lymphoid differentiation, we have isolated chicken TCF clones from a spleen cDNA library. Low-stringency screening with human probes as well as a polymerase chain reaction-aided strategy resulted in the cloning of a single chicken TCF (chTCF) gene. Sequence comparison revealed that chTCF contained a TCF-1-alpha-like N terminus, and a TCF-1-like C terminus. Furthermore, TCF-1 and TCF-1-alpha were more homologous to chTCF than to each other. We postulate that chTCF is the direct descendant of a single ancestral gene, which has been duplicated in mammals to yield TCF-1 and TCF-1-alpha.