Functional inactivation of Thyroid Transcription Factor-1 in PCCl3 thyroid cells

The expression of a fusion protein composed of the DNA binding domain of TTF-1 and of the strong repressive domain of the Engrailed protein (Engr HD) resulted in a dramatic loss of epithelial cell morphology and in proliferation arrest. These changes were reversed when the inhibition of endogenous TTF-1 was relieved. No change was observed when a similar fusion protein containing point mutations abolishing DNA binding activity (Engr HDm) was produced in the cells.